I was able to enjoy it as a stand-alone movie. I know a lot of people are saying "What about the other Avengers? What about Shield?" I thought about it, but it didn't bother me that much. I wanted to see how Tony was going to use his wits to handle this seemingly unbeatable bad guy.
I think this will be a problem for all future Marvel movies. The Avengers set the bar sooo high, that expectations are crazy.
Anyone, but Ms. Marvel. If Ant Man wasn't in the workings, him and Wasp would be my two big picks. Falcon is already rumored to be in Cap. I am going with a bunch of nameless characters and maybe Dum Dum as a bone to the fanboys.