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

Again, I haven't seen Civil War yet.

But looking at the 2 hero's progressions:
Stark, military contractor, turned into vigilante anti-terrorist. Initially distrustful of government agencies (particularly intelligence), eventually feels overwhelmed by the perceived threats, wants to play ball with governments to protect humanity. Feels some guilt in what's going on, and a drive to stop it.

Rogers- super-soldier, becomes modern government operative, becomes disallusioned with modern society as well as the government, increasingly distrustful of anyone but himself. Wants to give Bucky a pass for killing tons of people (including a bunch of good SHIELD personnel recently), because "he's Bucky".

I have a pretty tough time with Bucky, as would people who would have known, for example, the dozen or so people he killed in WS alone. If he kicked my buddy into an aircraft engine, I'd say the hell with Cap. Wouldn't care if he was brainwashed.