I just saw the Avengers as well. "spectacular" is the best word to describe it!
But,
In order for it to make any sense to the viewer, you MUST watch the movies: "ironman", "Thor", and "Captain America" (in that order, preferably) or else the movie won't make a lot of sense. The Avengers builds on and resolves a lot of elements from those movies.
On a more sophisticated note. I also recently watched 'The Mystery of Rampo" a Japanese movie from a few years back. This movie is in Japanese with English subtitles, but for those of you who can deal with that, I heartily recommend this one; it is THE most amazing storyline I have EVER come across!
It's set in Japan just before WWI. It's about a scholarly author whose story he's writing starts coming true in the newspapers almost as he writes it. He feels a strong bond with the heroine in his story, and becomes almost obsessed with writing her life.
Lines between reality and fantasy blur as he meets her and interacts with her. At one point he writes a sentence one of the characters is to say to the heroine, but the character pauses, turns and looks at the author (the camera), and firmly says: "no." then does something different
As for the ending, well I won't give it away, but I promise you: you will watch it and then say: "Wow. That blew me away. What the hell just happened?"
Netflix has this on DVD for those interested.