Is this the best comic book film adaptation of all time? It's certainly up there (IMO with Batman Begins and V for Vendetta, both of which, like Iron Man, actually have some plot). And from a physics geeky point of view, it's certainly one of the coolest. All the guys came out of the cinema wanting to be Iron Man, and most of the girls wanted to be with him.
Robert Downey Jr stars as a playboy genius weapons developer who gets kidnapped in Afghanistan by rebels and forced to build a super weapon. Most of the rest is fairly predictable, but it's great fun.