Every now and then, there is a role and an actor that meet in perfect harmony. Usually the actors are so perfect for the role, that when you hear they've been chosen for the part, one thinks, of course! Patrick Stewart as Professor Xavier was one of these serendipitous pairings. Tobey Maguire was a perfect match for the overly earnest Peter Parker, and when I heard Christian Bale would play Batman, I said, cool! These examples are all portrayals of super heroes.
Robert Downey, Jr. is the perfect character to play billionaire inventor and playboy Tony Stark. Unrelentingly honest and blunt yet charming despite his faults, Downey is Tony Stark. This is a fun one, and probably my favorite super hero movie yet.
There is a lot of humor, some intrigue, and a good bit of action in Iron Man. I did find a couple of noticeable flaws. Stark's heart problem is either badly imagined, or badly explained. The other problem is a paradox: it seems that there is a low-level message that weapons are bad (mmmkay?), so Stark will stop making them, except for the Iron Man exoskeleton, which is one of the most effective weapons ever created. But good. I subtract half a star for these issues, but that still leaves a solid 3.5 of 5 stars.