When I first heard about Marvel's crazy idea for a multi-film franchise I thought it was one of the silliest ideas I had ever heard. But somehow, without really trying to, I have managed to see all of the prequel films that build up to this film's main event, so I guess full credit (and box office returns) must go to the producers - the whole thing has been managed rather well.
For those keeping score at home, here is what I thought of the prequels:
Iron Man - excellent.
Iron Man 2 - disappointing.
The Incredible Hulk - not terrible but forgettable, I preferred the Ang Lee version.
Thor - extremely loud and silly, but watchable.
Captain America - even more silly, but took the premise and ran with it to entertaining ends.
Astonishingly, none of these films were aggressively stupid in the way that even the best superhero franchises tend to become after a while. So I had high hopes for The Avengers.
Hopes that turned out to be completely justified! The Avengers tells the story of all these guys finally meeting and eventually (spoiler alert) teaming up. As an adaption it is a great success, I am not sure the plot follows any particular existing story but it adheres much more strongly to conventional comic book structure than the typical film plot. All the explanation of who these characters are and where the came from has been neatly dealt with in previous films so The Avengers can get straight down to business.
The script is clever and Iron Man's quips are as witty as ever. The story is simple, but appropriate for the material. Personally, I could have stood to see more Hulk (the new guy playing him nails it, but there isn't enough time to flesh out the changes he is going through), and less Captain America however these are minor quibbles. Almost every detail is perfect.
Highly recommended if you like this sort of thing.