The Perfectly Cromulent Sequel: This is the wise and cautious choice. This is one where the creative team says "Let's do everything we did in the first movie but at 110 percent!," which translates to everything you did in the first movie at 85 percent. But that's enough for a huge opening weekend and a perfectly decent overall box office. No one can complain -- too much. Example: Iron Man 2
The Undercooked Sequel: Hey, did we mention we want the sequel for summer, two years from now? That's enough time for a script, right? I mean, you were working on something already, right? What? Well, don't worry: the kids are going to love it anyway. We'll just put in an extra $30 million in effects. No one will notice! Examples: Transformers: Revenge of the Fallen, Batman Returns, Men in Black II
The Better-Than-the-Original Sequel: You had to jump through studio hoops to get the first movie made, but now you have the box-office clout to do it your way. And your way is better! Hire that brilliant novelist to write the backstory! Level up your screenwriters and maybe your director! Toss in some respected actors (who are not too expensive and maybe need some work) for your protagonist to bounce off of! Get some special effects that aren't as cheesy as they were in the first film! You deserve it. So do the fans. Examples: Spider-Man 2, Blade II, Terminator 2: Judgement Day
The 'We Have No Idea What We're Doing' Sequel: This is what happens when you aim for the better-than-the-original sequel but miss, really badly, because (a) the filmmakers are in way over their heads, production-wise; (b) the filmmakers have no idea what made the first film popular and pick the wrong things to highlight; (c) key brilliant filmmakers are tossed and replaced by hacks; (d) no one really cares because there's just money to be made; or (e) some combination of any or all of the above. Result: a classic of bad. Examples: The Chronicles of Riddick, Highlander II: The Quickening, RoboCop 2
The 'We Always Envisioned It As a Trilogy' Sequel: The first movie's such a hit that the studio wants to make two sequels! But that's expensive, and they just want to pay for one and a half. No problem: you'll just shoot the next two films at the same time and put them out six months or a year apart. No one will notice that you've strung a single movie across two films and padded out the films with a bunch of incomprehensible subplots and in-jokes no one can figure out or care about. In fact, they'll love it! Examples: The Matrix Reloaded, Pirates of the Caribbean: Dead Man's Chest
Made your choice? Excellent. Now choose one of the three following three-quels.
The 'We Have Too Many Plots and Characters' Three-quel: Because nothing exceeds like excess. Or so you have apparently been ordered to believe by the studio. Examples: Spider-Man 3, X-Men: The Last Stand, any "We always envisioned it as a trilogy" third film
The 'We Don't Want to Admit We're Just Milking It at This Point' Three-quel: Look, everybody has bills to pay, okay? Examples: Terminator 3: Rise of the Machines, Blade: Trinity
The 'Let's All Try to Forget How We Messed Up the Sequel' Three-quel: You don't want to remember and neither does the audience. Examples: Batman Forever, Transformers: Dark of the Moon (one assumes), Men in Black III (ditto), the upcoming Riddick film (oh, God, please)
What? You're still around? For the fourth, fifth, and beyond, select from the following.
Ride the Gravy Train: You've got a franchise! Ride it until it grinds into dust! Examples: Every Star Trek movie between The Wrath of Khan and Nemesis
Book Series: Very much like Ride the Gravy Train, except you have the possibility that it won't just flab out at the end. But remember: the last book in the series? Two films. Examples: Harry Potter and Twilight series
Pull Out: Who needs an ensemble when everyone's just there to see Wolverine get pissed? Example: X-Men Origins: Wolverine
Prequel: All the stuff everyone liked -- but earlier! Examples: X-Men: First Class, Star Wars: Episodes I-III
Reboot: All the stuff everyone liked, all over again! Also darker and/or with jazzier camera angles. Examples: Star Trek (2009), Batman Begins
Note that with each of the last three, if you pull it off, you get a chance to start the sequel cycle all over again. And thus the Hollywood circle of life begins anew!
Well, until the third film (inevitably) disappoints everyone.
Hey, don't look at me like that. It's not my fault.