The Avengers is interesting as it unites characters from a number of other movies (a first?) to for a "super-team" of superheroes to save the Earth yada yada. However, it is terribly clichéd, the dialogues often vapid, and the plot resembles a sieve. That said, the whole point of the film appears to be a rather convoluted attempt at engineering a situation where the CG guys can have fun giving us a superhero war scene. And my, how they succeeded.
Watch the film for the battle scene towards the end. The rest is mostly dull.