Sure, the trailer got me excited for the movie. But that's a trailer's job, to get you into the movie; I always take them with a huge pinch of salt. Iron Man 2's trailer was pretty kick ass as well, remember? All too often, all the good parts of the movie are in the trailer and the rest of it is a big steaming pile of bovine excrement.
My default position on all superhero movies is that they are going to be mediocre at best, awful at worst. Then, when I actually see it and its pure triple distilled crystalised awesome - like Avengers was - I can be happily surprised.
Life in general has made me a natural pessimist. It's my default position in all things.