Megamind's main strengths are that it has a great cast (Will Ferrell, Tina Fey, Brad Pitt, Jonah Hill), and it's funny. Its main pitfall is that it's not hilarious. It's a chuckle movie, with maybe a few laugh-out-loud moments. That doesn't mean it's bad. No, as a whole, it is charming and cute (I really do not like using that word to describe movies, grr!). And I love Megamind. From the beginning, I was on his side, and it was obvious why he wanted (sort of) to destroy his nemesis, the heroic Metro Man. That guy is a douche. Will Ferrell is perfect for the voice of Megamind, and Brad Pitt as Metro Man is good, but he sounds like George Clooney, which just confused me. Seriously, I would not have known that was the Pitt had I not seen his name on the movie.
So, Megamind is charming and funny, but not top-notch.