I think IM3 has several things going for it:
- Shane Black’s script, which is especially suited to a smart, snarky main character like Tony Stark and the kind of people he likes to have around him.
- I actually think having Tony Stark out of the suit, experimenting with new tech, etc. was a good move after IM2′s repetitious robot-fighting. And the supposed whip-saw over the Iron Legion that some people didn’t like I would argue works much better in combination with CA:CW.
- Likewise, I think there’s better use of the secondary cast, especially with Pepper (although I would have liked to see more fallout from her getting super-powers).
- Going really far out on a limb, the twist with the Mandarin is actually a great idea. The original Mandarin, while having a neat power suit, is so rooted in nakedly racist Yellow Peril/Fu Manchu tropes that playing it straight would be unforgivable.