I went to see Iron Man last night with Mik and a few other comic book nerds I know. It was AWESOME!! Mik beat me and already has his own review up.
Looking at Comic Book adaptations, before this movie my favorite was Spider-Man 2, followed by X2, and then a less specific mixture of Spider-Man, X-Men, Batman Begins and Blade. I have to say that Iron Man trumped them all, hands down. Make sure you read The Ultimates and stay through the credits!