Go see The Avengers. ASAP. You will not regret it.
What, you want reasons? Fine. There's lots of great action, with more than a few good laughs. The humor tends toward slapstick and sarcastic wordplay, but this is a movie based on comic books, so that's to be expected. It dragged a little bit near the middle, but that didn't last long. If you don't want to take my word for it, take Howard Tayler's word for it. Or the general movie-going public's word.