Iron Man actually showed much more of his douchey side in the film. While it was entertaining seeing him rip Cap apart, it also took him down a few notches as a hero. Definitely got the best lines.
Captain America was kind of a ****** to Coulson. Dumb looking helmet. Still, great character. He really didn't get to show off as much as the others but perhaps that's fitting.
Thor made the mistake of being filmed in HD with distractingly bad hair extensions. Could have used the helmet to help cover that up. Also, got owned by Hulk... hard.
Black Widow was cute, but even with her Buffyesque upgrade ScarJo will never quite be convincing as a former Russian spy. At least she didn't try an accent.
Hawkeye was actually pretty kickass as a mind-controlled Loki goon, but that doesn't count for the Avengers. He's a filler character, but a good one.
Hulk was the star though. Banner was easily the most likeable human character out of the whole bunch. When he finally did Hulk out, nothing could really stop him. The best they could do was distract him off the helicarrier, but when it came down to Loki the rest was cinematic history. He ate up that film in the short amount of screentime he actually had. Nothing but win.
