As a rule, superhero movies get better when it comes time to make the sequel. Without the origin story to clog up the first half hour, and without the need for the hero to announce a statement of purpose in the last half hour, the filmmakers are actually free to... you know... make a movie. Sam Raimi's Spider-Man 2 was a perfect cinematic representation of what Spider-Man should be. The Dark Knight was the complex study of heroism that Christopher Nolan has probably always wanted to make. It's unfortunate and confusing, then, when you discover that Iron Man 2 is somehow less fun and less action-packed than its predecessor.

Which is not to say that it doesn't have its fun moments, but most of those are reprisals of what made the first Iron Man movie such a sparkling surprise. Robert Downey Jr. and Gwyneth Paltrow effortlessly revive their sexy, loving, bitchy repartee from the first film; Jon Favreau continues to provide understated comic relief; and Samuel L. Jackson reprises his post-credits cameo from the first film (much more about that later) as a superspy who is kind of the Biggest Fanboy in the Universe.

And the new additions to the cast keep that same winking charm. Don Cheadle's James Rhodes has a depth—a clearly defined conflict between his duties as a soldier and as the best friend of Downey's Tony Stark, a billionaire industrialist who has suddenly stopped making weapons for soldiers—that evaded Terrence Howard in the same role last time around. Sam Rockwell's Justin Hammer alternates between appropriately campy menace and genuinely frightening envy as a tech manufacturer who knows he simply can't match up with Stark's genius. And Mickey Rourke's Ivan Vanko, a mad Russian scientist who holds a secret from Stark's past, is a menacing, physical foe. Only Scarlett Johansson seems out of place; as a superspy, she aces the physicality of the role—in a black Lycra jumpsuit, she whirls around her opponents like an ice skater before bouncing them off the ground—but mentally, her acting strategy seems to consist of a furrowed brow while all the banter flies around her.

So the parts are there for an intelligent superhero movie. Why don't they all work together? It's pretty simple: The plot for the damn thing is so unintelligent and perfunctory that it drags everything down. Vanko wants revenge against Stark for some past transgressions. Rourke plays him as a ruthless, intelligent man. So what does he do? He charges, bull-like, at Stark... twice... without devising anything remotely resembling a plan, leading to a climax that feels like a warmed-over rerun of the first film.

Stark claims to have "privatized world peace," and he is wasting away from a disease caused by his own technology. Besides a few funny, genuinely moving scenes where Downey manages to squeeze charm and peril from both of those developments, he spends an inordinate amount of time having a dumb fight with his best friend simply because the middle of the movie would be a swamp of exposition without it. And then he wanders around, aimless, for a good while longer, dealing with his daddy issues before he can get back to kicking ass and taking names.

There's a lot of talking here, and really only three (admittedly gargantuan) action pieces to liven things up. Part of the problem of Iron Man 2 is that the film has to deal with the repercussions of the post-credits scene from the first Iron Man movie, when Jackson's superspy Nick Fury tries to recruit Iron Man for the Avengers Initiative, a superhero team that will presumably protect America from grave threats. Too much of Iron Man 2 is a response to that scene and an obvious build toward the expanding slate of Marvel movies—next year will see the debut of the Thor and Captain America movies, with an Avengers movie following the year after that—that would be meaningless without the metaknowledge that Marvel is planning a team-up movie in the near future. There's no payoff for any of it here, and the movie concentrates so much on future franchise developments that the actual climactic battle is a huge disappointment.

Which is not to say you shouldn't see it. Odds are, you'll see it anyway. Iron Man 2 has enough clever acting, sly humor, and over-the-top action to make it a fine kickoff to the summer movie season. But it's all kickoff and very little kick-in-the-pants, with too much expository lifting where there should've been more tons more fun. recommended