You can probably use D&D alignment to think of interesting character aspects of Marvel characters.
- Captain America is fundamentally on the Good axis, but experiences conflict on the Law vs. Chaos axis in order to seek the Good
- Iron Man is fundamentally Neutral or even Chaotic on the order axis (if you consider a fundamental part of his character his individualism), and his character development (if you go all the way back to Iron Man 1) is about the good vs. evil that is inherent in his individualistic power seeking. Haven't seen it yet, but thing about Civil War and some of the ways the character gets more "boring"/"predictable" is that once Tony Stark become sort of more unambiguously good, you have to go back to the original question of whether he is neutral/chaotic vs. lawful in order to have a character conflict that is interesting for him to have to resolve.
- This of course sets up the premise of Civil War, as it's framed as two good characters falling on different sides