Far and away the best film in George Miller’s post-apocalyptic series, “The Road Warrior” occupies roughly the same place in this trilogy as Sergio Leone’s “For a Few Dollars More” does in the “Dollars” saga — which is to say, it showcases the filmmaker and his collaborators at the peak of their invention, expertly balancing wild ambition against storytelling restraint. Set some time after “Mad Max,” in a time and place that’s even bleaker and more uncivilized, “The Road Warrior” is a bigger, tougher, faster, more spectacular film than the original, but utterly disciplined and focused, never allowing itself to devolve into a series of set pieces as the third movie, “Mad Max Beyond Thunderdome,” often did, and never trying too hard to convince us that its hero (Mel Gibson) was still a decent guy at heart. It also features the best action in the series; that final pursuit through the desert, which I cited in a Salon slide show on great car chases, is simply one of the finest pieces of filmmaking produced in any country, by any filmmaker. And the final, dark twist is still a stunner.

This is a bit of an unexpected choice for me, because while I respect both “Before Sunrise” (1995) and “Before Sunset” (2005), they never struck the deep chord with me that they did with a lot of viewers; I remember panning the original film pretty harshly, as a matter of fact, because I thought the tone and dialogue were too unmodulated and felt so “written” that they worked against the naturalistic performances and atmosphere. Over time, though, director Richard Linklater’s quiet ambition has grown on me. There has never been, and probably never will be, another romantic comedy as stripped down, dialogue-driven and matter-of-factly intellectual as these two movies. It’s a play of ideas that just happens to take the form of a very long “meet cute” scene. And in a strange way, the second film bears the same relation to “Before Sunrise” as many of the other great sequels on this list, in that it teases out, examines and complicates themes explored in the first movie, and adds all sorts of emotional colorations that weren’t present the first time around. The original is a terrific portrait of 20-something innocence; the follow-up is about maturity and disappointment, and learning to live with both while fanning the embers of hope and wonder. Although in some ways the very prospect fills me with dread, I would be curious to see what Linklater could do with a third film — though he should probably wait a while to do it.

Even viewers who adored the original “Star Wars” — which I’ll always consider “the first film” even though it’s officially labeled “Episode IV” — were surprised by the richness and confidence of this sequel, which was written by Leigh Brackett (“The Big Sleep”) and Lawrence Kasdan and directed by George Lucas’ film school mentor Irvin Kershner (“Loving”). It has the slightly silly majesty of the original film — maybe more of it, thanks to Yoda — plus an intriguingly dark undertow, a downbeat finale and a touch of romance. More so than any other film in the saga, it feels like an old movie — the sort of crowd pleasing yet subtle artful spectacle that a studio might have unleashed in the 1930s or ’40s. It’s also the only one of the six films that one can unabashedly embrace without having to rationalize away egregious flaws. Every scene, every performance, every effect, every moment feels just right.

Last year’s “Toy Story 3″ was an entertaining and in some ways affecting movie, and definitely a legitimate heir to the other two films in the series. But I was a bit underwhelmed by it, and it wasn’t until I rewatched the second film that I figured out why. “Toy Story 2″ has the most exciting action and most affecting story of the three films, and teases out the multifaceted nature of the toys-as-metaphor much more imaginatively than the other movies. (They are at once children and parents, people and pets; their exact role shifts depending on where we are in the story.) I’d probably consider this the best film in the “Toy Story” series even if it didn’t have … Oh, dear … I don’t think I can ever describe it in detail because it’s so affecting that it’ll wipe me out. You know the scene I’m talking about. It’s just devastating.

Here’s the funny thing about “Aliens,” writer-director James Cameron’s follow-up to the 1979 Ridley Scott original: Although it extends the personal story of Ellen Ripley (Sigourney Weaver) and gives her a sense of personal closure and redemption, if you just look at what happens on paper, it almost seems like more of a remake than a second chapter. It has more or less the same setup (a distress signal that turns out to be a company-devised trap) and the same central horror movie dynamic, pitting an intelligent, principled heroine (Ripley) against a bunch of overconfident, ignorant people whose smug certitude will prove to be their death warrant; it even has a race-to-the-finish finale, juxtaposed against the impending detonation of a nuclear bomb. Yet the tone is so different from the original that it deserves to be considered as a legitimate heir to “Alien.” And it’s the first of many examples of an “Alien” sequel delivering certain core (or gore) elements while playing around with form and tone. Where the original was, as Scott cheerfully admitted, basically a very expensive haunted house film with sci-fi trappings and tons of Freudian nightmare imagery, this one is part war movie, part western, with a setup that evokes a World War II combat picture and a number of images and situations that evoke the cavalry westerns of John Ford. It’s also the most cathartic and emotionally satisfying of the “Alien” films — not to mention one of the greatest action pictures ever made.

I’ve already written extensively about this masterful horror satire in a Salon slide show and a video essay, so I won’t go into too much detail here; suffice to say that this follow-up to George A. Romero’s “Night of the Living Dead” (1968) is not just a greater film in every way, but one of the great films of the 1970s, a smashingly effective horror and action film that also has elements of slapstick comedy, domestic drama and social satire. Although horror filmmakers have been using the genre to critique real life ever since the medium’s inception, “Dawn of the Dead” still managed to expand the genre’s possibilities, simply by virtue of what it was and how it was made. It was a small movie that felt, and thought, big: an independently produced horror flick that became a cult hit, inspiring mainstream studio productions to take more chances with tone, theme and structure. “Dawn” also greatly upped the ante in the gore department, boasting makeup effects by Vietnam veteran Tom Savini that were at once horrifying, ludicrous and strangely sad. The most haunting sections of the film have nothing to do with zombies; they show the mortal characters living a sad facsimile of civilized life in the film’s main setting, an abandoned shopping mall. The sense of dislocation, of going through the motions even though the world has quite literally collapsed, feels less like a typical horror movie lull than a section from the great horror film that Michelangelo Antonioni never got around to making.

Is it cheating to include this deliriously entertaining swashbuckler? I’ll let the readers decide. “The Four Musketeers” is not a traditional follow-up to an original hit (1973′s “The Three Musketeers”) but an improvised continuation, cobbled together from footage that was excised from the first movie to keep it from bloating into a four-hour epic. Yet the result seems to flow so organically from the original that, as is the case with the first two “Godfather” movies, the whole saga blends together in the mind. Subtitled “Milady’s Revenge” in some markets, it follows the Faye Dunaway character, Milady de Winter, as she tries to get payback against the hero D’Artagnan (Michael York) by luring him into an unnecessary attempt to “rescue” his men; the plot grows increasingly tangled from there, with Milady and Cardinal Richelieu (Charlton Heston) proving worthy adversaries for the title characters. Directed by Richard Lester (who helmed the first movie as well as two great Beatles films, “A Hard Day’s Night” and “Help!”), “The Four Musketeers” is romantic, thrilling, slyly funny and deftly paced — a rare example of a purely money-grubbing follow-up perfectly capturing the spirit that made the first film such a success. (It also had an effect on Hollywood bookkeeping, though; because producers Alexander and Ilya Salkind effectively made two films for the price of one without warning the cast, actors’ contracts now include what’s known as a “Salkind clause,” stipulating that if the filmmakers create more than one movie based on footage from a single production, it must be treated as a separate film for paycheck purposes.)

This pitch-perfect western epic might be the most controlled and perfect film that Sergio Leone ever directed. It shows off his masterful use of screen space and clever grasp of black comedy even more effectively than the original “Fistful of Dollars,” but it’s a lot more contained and on-point, and thus more accessible, than the third film in the trilogy, “The Good, the Bad and the Ugly.” The movie also complicates the trilogy’s hard-bitten, nihilistic hero, the Man With No Name (Clint Eastwood), without tipping over into sentimentality as the third movie sometimes did (though the third film is great in its own right). Come to think of it, what’s most intriguing about “For a Few Dollars More” is the fact that, when you get down to it, the movie doesn’t really have a bad guy. Eastwood’s character is ruthless but more of an antihero than a villain; his rival-turned-partner, Col. Mortimer (Lee Van Cleef), is on a mission of revenge, looking to kill the outlaw who raped his fianc

How effective is “The Godfather: Part II”? So effective that within a couple of years of its release, it had already been accepted not merely as a more expansive, ambitious, nuanced follow-up, but a legitimate extension of the original’s story, so memorable in its own right that it seemed to retroactively deepen the original “Godfather.” (The two movies were combined in a 1978 TV miniseries titled “The Godfather Saga.”) “The Godfather: Part II” is also a fantastic example of how to repurpose material from a source novel that was omitted in the writing of the first film. Director Francis Ford Coppola and his co-screenwriter Mario Puzo (author of the original book) hit on an ingenious way to use all the bits that came before and after the narrative of the first “Godfather.” The film flashes back and forth between the childhood of mob boss Don Vito Corleone (Marlon Brando in the original, Robert De Niro here) and the troubled reign of his successor, Michael (Al Pacino), comparing and contrasting two eras and two crime bosses, showing the difference between 19th and 20th century mind-sets, and demonstrating that Michael has his old man’s ruthless tactical genius but none of his warmth or sense of proportion.

“The Godfather: Part II” is bigger than the first film in every way, boasting more locations (including elaborate re-creations of early Sicily and New York in the early part of the century and Cuba and Las Vegas circa 1959) and a more pointed critique of American capitalism. It also (partly) addresses a legitimate complaint against the original, that the violence caused by the Corleones’ criminal enterprises is never shown affecting anyone but other criminals and people who chose to become involved with the Corleones. The sequel shows much more collateral damage to innocents, including cops who die in a street shootout and a prostitute who’s mysteriously found dead in the bed of a senator (G.D. Spradlin) that Michael wants to control. The movie’s final shot is so devastating that it rendered the eventual third film, “The Godfather: Part III,” superfluous.

One of the most sheerly pleasurable sequels ever made, “Bride of Frankenstein” is also a great example of a director feeling his oats because of an original movie’s box office success and building on it in all the right ways. For all its visual elegance, James Whale’s original “Frankenstein” (1931) was a pretty straightforward affair, presenting a modern version of Mary Shelley’s novel with a straight face. The follow-up is a dark comedy; it extends the original’s story and themes while adding generous doses of humor that was, for its time, daringly irreverent, even bitchy. William Hurlbut’s screenplay creates a new scientist character, Dr. Septimus Pretorius (Ernest Thesiger), who’s essentially Dr. Frankenstein (Colin Clive) without any trace of sympathy, or any qualms about the ethics of playing God. He’s already created life many times. His prior masterworks include “homonculi,” miniaturized humans who are like little toys with pulses: a queen, a king, an archbishop, a devil, a ballerina and a mermaid.

This film’s creation sequence is more spectacular and poignant than the original’s, with Pretorius enlisting the monster (Boris Karloff) to kidnap Frankenstein’s wife, Elizabeth (Valerie Hobson), to blackmail the doc into helping him create a bride for the creature. Her final appearance in the form of Elsa Lanchester — all decked out in a flowing gown and a hairdo that looks as though it was styled with lightning — is brilliant. The movie also contains many images that have become powerfully (and wrongly) associated with the original “Frankenstein” in the public mind, including Pretorius’ insane shrieking during the creation scene and a poignant encounter between the creature and a blind hermit (O. P. Heggie) that became the basis for a great routine in Mel Brooks’ “Young Frankenstein.”