Robert Downey Jr. IS Iron Man! And I don't just mean that he plays Iron Man. I also mean that he is what makes this franchise spark. Without Downey - his wit, his irreverence, his tortured soul - the whole Iron Man film series would have little reason to exist. He proves that again with "IM3." Sure, there are explosions and chase scenes galore, but the best moments are when Downey is just talking. He joshes with a kid he meets. He riffs to Gwyneth Paltrow. He rambles to himself. Downey's Tony Stark faces the fall-out of medical experiments gone away - experiments meant to help people with injured or lost limbs regenerate them. Unlike "Terminator 2," whose robot villain could repair himself, "IM3" doesn't set up understandable rules for what can or can't kill these regenerating people; it seems to shift. Two great actors, alas, fade in this comic-book world. Guy Pearce underplays his role as Stark's nemesis; he should have followed Javier Bardem's James-Bond lead and gone over the top. Same goes for Rebecca Hall, bland as an is-she-good-or-bad Stark acquaintance. But all is forgiven when Ben Kingsley is onscreen, and you'll have to see the movie to fully appreciate why.

- KRISTINA DORSEY