1. Aliens (1986)
Some film sequels are "necessary" in the sense that they're planned franchises from the beginning, continuing an at least partially incomplete story. (The Empire Strikes Back comes to mind.) But most sequels are rushed into production when their progenitors make money, and are driven less by story necessity than by the desire for a quick payout from an assumed built-in fan base. It's a rare stand-alone sequel that finds its own feet as something other than a loud, pandering redux. Still, cinema occasionally manages to rise to the occasion with something like Aliens, a slick, thoroughly enjoyable actioner that was in no way required or even set up by Alien. Ridley Scott's terrific 1979 original was an atmospheric horror movie, but Aliens managed to repurpose its elements into a shoot-'em-up thriller without disrespecting its parent film. It's almost a model sequel: bigger and faster, but not dumber, and not just a rote copycat of the first movie. Later Alien sequels weren't nearly as smart.
2. Psycho II (1983)
The recurring theme of the "unnecessary but good" sequel is "It could have been worse," and that's never been truer than in the case of Psycho II. For proof, check out the novel Psycho II written by original Psycho author Robert Bloch (notoriously loathed by Universal), who jettisoned everything familiar in favor of a leaden attempt at critiquing 1980s slasher films. Richard Franklin's unrelated film Psycho II is leagues more reverential—filled with clever callbacks, it's really more of an homage—and it handily avoids so many of the traps Bloch apparently assumed it would fall into, such as merely upping the gore for modern audiences. Instead, Psycho II deliberately takes its time, expanding on its predecessor's mind games, and even adding revealing new layers: Norman Bates's slow unraveling at the hands of various tormentors is handled surprisingly sympathetically, giving him a depth that actually adds to his character. Although it's guilty of one too many twists (and the final, blasphemous reveal serves no purpose other than opening the door to a franchise full of diminished returns), the film itself is a worthy successor made by people who obviously know the original inside and out. So it isn't as good as Hitchcock. But who is?
3. Toy Story 2 (1999)
Pixar Animation made a strong leap from shorts to features with 1995's Toy Story and 1998's A Bug's Life, but the studio's third project, Toy Story 2, raised some eyebrows; less than five years after its debut full-length, it looked like Pixar was already out of ideas, and heading back to the well for a Disney-style cash-in. (It didn't help that Disney raked in the dough for 1994's The Return Of Jafar, and spent the next decade watering down its brand with disappointing, low-rent sequels to its big-screen successes.) And yet Toy Story 2 actually improved on its predecessor, with better animation, tighter storytelling, more resonant themes that tapped into human emotion as well as toy emotion, and just as much humor as the first film. Pixar was mildly well-regarded after its first two films, but Toy Story 2 was the mega-hit that made its name.
4. Texas Chainsaw Massacre 2 (1986)
There was really no need for Tobe Hooper to make a sequel to his '70s grindhouse classic The Texas Chain Saw Massacre, and even he seems to acknowledge that with his sequel. First the original's cannibal family returns as cartoony Reagan-era entrepreneurs. Then, in the back half, the cartoony tone gives way to gore that challenges even the most hardened Fangoria readers. It's a film with the bloody integrity to ask horror fans, in the wake of all those slasher films the original inspired, if they really want to see things pushed as far as they can be.
5. Gremlins 2 (1990)
Joe Dante's original 1984 film Gremlins wasn't short on satire, but for this sequel, he pumped the satire with steroids, letting the little monsters run amok in a state-of-the-art office building run by a Trump-like tycoon, and serving as cartoon proxies to send up whatever he felt like taking on. Audiences didn't bite at the time, but it's no surprise that it's become a cult classic.
6. Rocky III (1982)
It's tough to make a strong case for Rocky III being a great movie—it's definitely inferior to the 1976 original, and plenty of movie fans don't even think that film is all that fantastic. But judged against other Sylvester Stallone-directed sequels—a lowly genre that also includes Rocky IV, Rambo, and Staying Alive—Rocky III manages just the right mix of rousing sports-movie magic and highly entertaining cheese, making it the second most essential Rocky film. Credit for the latter mostly belongs to Mr. T, the A-Team star who was unsurprisingly adept at playing a trash-talking, Mohawk-sporting tough guy with a bad attitude. (The rest of the credit goes to the all-time montage classic "Eye Of The Tiger.")
7. Babe: Pig In The City (1998)
The first Babe was a sweet-natured family film about a talking pig living on a loveably eccentric farm. The sequel, Babe: Pig In The City, was something else entirely. A throwback to old-school kiddie-tainment that wasn't afraid to put a real fright into youngsters, Babe: Pig In The City plays into common childhood separation anxieties, taking Babe away from his stricken "father" Farmer Hoggett and placing him in a grotesque circus headed up by Mickey Rooney as the world's creepiest clown. It's no shock that Babe: Pig In The City sank at the box office, but it's still a worthy sequel that stands apart from its much-different predecessor.
8. Terminator 2: Judgment Day (1991)
Awkward as it may be in light of better science-fiction/action flicks, 1984's The Terminator was a completely insular movie, albeit one laden with a cheesy soundtrack, self-conscious steampunk elements, and embarrassing '80s hairdos. But Terminator 2: Judgment Day couldn't exist without it, and it surpasses the bare-minimum requirements of a sequel by actually expanding on the overarching story in meaningful ways, masterfully injecting tension, and knowing to play the over-the-top action for comedic as well as dramatic effect. Though it's since developed into a lucrative franchise, for many, the series peaked in the second installment, no matter how many times the characters shout amid gunfire, "Get down!"
9. The Color Of Money (1986)
The really surprising thing about the sequel to the classic Robert Rossen flick The Hustler isn't that it was any good; it's that it was made in the first place. While the 1961 original, featuring a stunning young Paul Newman and a riveting Jackie Gleason as dueling pool sharks, was widely considered a great film, people were hardly beating down the doors of their local cineplexes for a sequel, particularly a quarter of a century later. But Martin Scorsese had nothing to do that week, and Tom Cruise was looking to do to nine-ball what he'd just done to jet fighters and was about to do to mixed drinks, so America was surprised when it wound up watching a solid sequel to a movie it had largely forgotten. The Color Of Money is capably directed, occasionally thrilling, and not the worst thing Tom Cruise has ever done. Besides, it won Paul Newman a long-deserved Oscar.
10. Mad Max 2: The Road Warrior (1981)
George Miller's 1979 post-apocalyptic police thriller Mad Max was a breakthrough hit in Australia, so the leap to a sequel was no shock. The surprise was that the producers decided to aim the sequel straight at the American market, which had barely noticed the original. Dropping the Mad Max 2 from the title and largely removing the relatively unknown Mel Gibson from the trailers, U.S. distributors marketed The Road Warrior as explosive non-stop action—which is exactly what it was. The gamble worked: American audiences not only turned the movie into a huge international smash, but went back to investigate the original, laying the groundwork for the series to become an institution. The way Miller refashioned his original film to go even deeper and darker into the post-oil-peak world was compelling; the way he managed to make it into one of the biggest action films of all time was astonishing.
11-12. Evil Dead 2: Dead By Dawn (1987); Army Of Darkness (1992)
The original Evil Dead, released in 1981 and directed at a cost of about six bucks by a young Sam Raimi, didn't make much money, but it was widely beloved by a certain type of horror fan. Six years later, armed with a bigger budget but unsatisfied with the way the original had turned out, Raimi took another shot at it, and Dead By Dawn isn't so much a sequel to the original as it is a reboot-cum-remake. It plays fast and loose with the continuity, but that's nothing compared to what it does with the overall tone of the movie: What differentiates this gory-mayhem-in-a-remote-cabin-in-the-woods horror flick from the gory-mayhem-in-a-remote-cabin-in-the-woods horror flick that preceded it is its hellacious sense of humor. Chucking nightmare-fuel horror conventions in favor of slabs of slapstick, while maintaining all the gore and then some, Evil Dead 2 improves on its predecessor in every way by refusing to take itself seriously. And the all-goofy, joyously camp, endlessly quotable third sequel, Army Of Darkness, is just plain fun.
13. Dawn Of The Dead (1978)
It's now almost unthinkable that George Romero's zombie mythology ever wasn't a franchise, but back in the 1970s, his gripping, low-budget 1968 film Night Of The Living Dead was barely a memory in America. For one thing, the original film didn't leave much for him to work with—not only (spoiler alert for a 40-year-old movie!) were all the characters dead, but they were, in the words of the local sheriff, all messed-up. For another, Romero had no intention of making his zombie movies anything like an institution; he'd moved on to other varieties of horror, and had to be convinced by Dario Argento—one of several European admirers of Night Of The Living Dead—to return to the theme. Luckily, Argento's pep talk worked: Romero cranked out the script for Dawn Of The Dead in less than a month, ramped up the social commentary something fierce, rented out the Monroeville Mall, and made zombie history. Dawn shifted Night's small-stage shock-horror to global-apocalypse levels, and the living dead would never be the same again.
14. A Better Tomorrow II (1987)
Hong Kong action maestro John Woo first made a name for himself on the international scene with 1986's A Better Tomorrow, a conventional cop thriller made special by Woo's balletic, Sam Peckinpah-inspired gunplay and Chow Yun-fat's uncanny charisma in the lead role. Woo tried to top himself with A Better Tomorrow 2, and he did, though he reputedly hates the film, largely due to disagreements with producer Tsui Hark, who had a hand in the final product. (It was cut from its original three-hour run time down to 105 minutes.) In spite of the incoherent plot, Woo manages several memorable sequences, including a spectacularly bloody climactic shootout at a mansion that rivals Peter Jackson's Dead/Alive for most gore in a confined space.
15-16. Police Story 3: Supercop (1992); Drunken Master 2 (1994)
As a general rule, Hong Kong action films have a higher rate of success with sequels than their American counterparts, mainly because they raise the stakes. Where American sequels have a "more of the same" attitude, Hong Kong films are about "more of the same, only more," which sets the bar that much higher as a franchise progresses. There's a reason why U.S. distributor Dimension Studios skipped right on past Jackie Chan's Police Story and Police Story 2 to release the spectacular Supercop in 1996: It's funnier than its predecessors, it has more action, and it features the magnificent Michelle Yeoh jumping a motorcycle onto a moving train.
Similarly, Chan's 1978 breakthrough Drunken Master revealed his unique ability to meld kung-fu with Buster Keaton-inspired physical comedy and stunt work, but it was Drunken Master 2 (a.k.a. The Legend Of Drunken Master) that capitalized best on the sheer scope of his abilities. Among the highlights: A climatic showdown at a fiery steel mill (where Chan literally walks over hot coals for your entertainment) and a famed restaurant scene where he and an older man take on a hundred axe-wielding assassins.
17-19. Quatermass 2 (1957); Quatermass And The Pit (1958); Quatermas (The Quatermass Conclusion) (1979)
British writer Nigel Kneale made one of TV's first forays into the chilling "cosmic horror" tales pioneered by H.P. Lovecraft with the 1955 miniseries The Quatermass Xperiment, the tale of a government rocket scientist who discovers that an alien capable of absorbing all life on Earth has secretly hitched a ride on a returning space probe. Though Kneale's story was fueled by the Lovecraftian notion that there may be some things so awful that humanity could never hope to defeat them, the intelligence and humanism of Prof. Bernard Quatermass (Brian Donlevy) wins the day, and the monster is destroyed before disaster can occur. Experiment was a huge popular success, and sequels were inevitable; they eventually included several more TV serials and film adaptations, but Kneale's smart, nuanced, often gloomy scripts kept the series from becoming stale. The series became hugely influential on the science-fiction field, lending ideas to Doctor Who, The Twilight Zone, The Thing, and Invasion Of The Body Snatchers, among others. The best of the sequels is probably Quatermass And The Pit, in which the professor uncovers a shocking secret about human evolution after the discovery of a spacecraft buried in the ground underneath London.
20. Before Sunset (2004)
The ending of Richard Linklater's 1995 dusk-to-dawn romance Before Sunrise was bittersweet perfection, the ambiguous end to a magical evening in Vienna between two hyper-intelligent young people, an American (Ethan Hawke) and a Frenchwoman (Julie Delpy) who met on a train. Viewers were left with the tantalizing question: Did the lovers meet again at the same place one year later, as they promised, or was this the last they'd see of each other? It seems foolish to provide an answer, but the miraculous follow-up, Before Sunset, is somehow even better. In the nine years since they last met, Hawke and Delpy have changed—Hawke, for one, has a wife and child—but their brief reunion in Paris brings up old thoughts of what might have been and what might still be. Linklater again ends with a perfect question mark, but if he, Hawke, and Delpy want to pick up the thread another nine years from now, they won't be second-guessed.
21. The Godfather Part II (1974)
Perennially ranked as the greatest sequel of all time—not to mention one of the greatest films of all time—The Godfather Part II isn't merely a worthy addition to Francis Ford Coppola's original: In many ways, it's the superior film. By juxtaposing Michael Corleone's struggles as the new head of the family with Vito Corleone's hardscrabble rise to power, the film enriches the original's theme of "the sins of the father are visited upon the son" and provides evidence of how Michael's pride guarantees his downfall, giving the entire saga a mournful undertone that elevates it from mere mobster movie to something approaching Greek tragedy. But beyond such critical bloviating, The Godfather Part II is also an endlessly entertaining film, full of memorable scenes, masterful performances, and layers that reward repeat viewings. It's the rare follow-up to something that's already damn near perfect, and it not only establishes a case for necessity, it actually makes its progenitor feel incomplete.