As of this writing, 36 movies have been made based on Marvel comic franchises. Needless to say, not all of them are going to be home runs. Some of them, however, have proven to be quite enjoyable. Here's a list of the top 5.
5) Iron Man 3
Iron Man 3 may have divided long-time fans of the comic series, but it still managed to make a boat load of cash, and with good reason. Even despite the Mandarin twist, the movie had some of the best humor and action in any Marvel movie to date.
4) Spider-Man 2
Sam Raimi took everything that was good about the first Spider-Man film and turned it up to 11. Somehow, Spider-Man 3 also seems to have made the second installment retroactively better. Go figure.
3) X2: X-Men United
Proving that he could handle an all-star cast of superheroes, Bryan Singer deftly juggled several different developing story lines into one fluid narrative with plenty of action to boot. It's too bad the same can't be said for X-Men 3, but at least Singer's back on board for this year's Days of Future Past.
2) Thor
I have to admit, when I first heard that Thor was going to be made into a feature film I was surprised that Marvel would choose such a seemingly bizarre choice (although the announcement of Guardians of the Galaxy and the possibility of a Doctor Strange film have since made Thor seem somewhat safe), but they absolutely managed to pull it off.
1) The Avengers
Come on, like you didn't know this was going to be number one. The Avengers managed to do what no other film has done before and successfully merged four different film franchises into a single film experience. It was also tons of fun, which helped quite a bit.