The best superhero/comic book movies are the ones that focus on the main characters, not the special effects or the explosions or any such giddy nonsense; you definitely need some of that, but walking that very careful line is something few movies can do, and Iron Man is one of those movies.
To be honest, when I heard that an Iron Man movie was coming out, the first thing I thought to myself was "really? Iron Man? Have they run out of more well-known superheroes to make movies out of?" Even though I found out afterwards how important and long-running Iron Man really is, I declared myself corrected right around the time Tony Stark finished fashioning a crude prototype suit in an Afghani cave. Robert Downey Jr. made Tony Stark a completely believable character, and the audience has to come to love him; unlike Peter Parker, Tony Stark has made a name for himself already, but the horrors he ends up seeing that he turned such a blind eye to earlier were too much to handle. This is an origin story, but that doesn't make Tony's determination to right a few wrongs in the world using a highly-advanced, racecar-paintjob-inspired suit any less cool.
I intend to see this movie again, if only finally see the hidden scene at the very end, but even without that extra ending Iron Man was a movie that exceeded all audience expectations, and by audience, I mean me and the other nine people I saw it with. We couldn't shut up about how good it was for days. You won't either if you haven't seen it yet. Wait, why haven't you seen it yet? STOP READING THIS AND GO SEE IT!!!