re: Iron man has been pretty unimpressive since his first movie

To be fair, I saw him as very positive in the first Avengers movie.
-working on Arc tech to make his building energy self-sufficient.
-saved Cap's arse vs Loki, after being brought into the loop, but not formally brought into the team.
-was suspicious (rightfully so) of SHIELD's motivations behind their work on the Cube.
-pushed Cap to not just follow orders, told him they were not soldiers

As for the hero stuff-
Took out more aliens in New York than the others, except possibly the Hulk and/or Thor.

Made the informed sacrifice that stopped the invasion fleet, with the nuke (that shut down their command and control, before the rift was closed).

Granted, I haven't been able to go see Civil War yet, don't know how he impacts that.