There were quite a few good movies in 2010, a few great ones, and quite a few that would go into Peter Travers Scum Bucket. Now, I never got to see Piranha 3D so I might be way off base but my personal pick for best picture would be The Town. It's not quite as good as Ben Affleck's first
turn as director in Gone Baby Gone but didn't require more than one viewing to fully understand if the movie was a dream or just a commentary on architecture.
Nobody guessed The Town specifically so from the list of submitted movies the winner is Mark of the The Green Card blog with his pick of Scott Pilgrim vs. The World.
There's nothing quite like it and it makes the director's previous movie, Hot Fuzz, feel calm and relaxing in comparison. Congrats Mark!