With as much as I am a Marvel fan, I have found not going in with high hopes has served me well. I just sit back and enjoy the ride.
That's generally the best approach to take with any movie, Marvel or otherwise.
I've gone to see each Marvel movie with a single expectation: to be entertained for a couple of hours. And so far, I've not been disappointed, with the first Iron Man and Avengers being my favorite of the films.
I was even able to enjoy Man of Steel and the prequels simply because I didn't hold any fanboy notions of what those films should have been. Granted, they certainly could have been better, but I wasn't pissed that I'd wasted my money to see them, as I was indeed entertained for the length of the films.
I think this bit I saw on my Twitterfeed earlier today sums it up:
DC: Superhero movies need to be gritty and realistic and serious.
Marvel: "runs by wearing a lampshade"