Iron Man 2
The second Iron Man is also great. I think it is more or less as great as the first. In different ways though. The first one kind of sets up how this stuff is going to work. And then this one kind of sets it up forther in the same theme as in the second part of the first movie. Most of the MCU movies will be in the theme of something beats them, and then the hero or the heros beat it in the second part.