Yah! Time to tell everyone why they're wrong
The Boondock Saints 2: This isn't quite a mass-hated movie but a lot of fans of the original hated it. A very fun and stylistic movie that I loved.
Matrix Trilogy: Like many, I was confused about what the hell happened to The Matrix. Then, a few years ago, I watched all three in a row on a day. A LOT of what was confusing and didn't make sense became clear once I saw them for the second time in a row.
Battleship [http://www.escapistmagazine.com/forums/read/18.400271-Battleship-Popcorn-flick-or-brilliant-satire#16444032]: ...alright, not really but only kind of just so I can break out my conspiracy theory again

I didn't hate it so I'm counting it dang it!
Sucker Punch: That additional scene added to the DVD/Blu-Ray I think completely changes the movie. Unfortunately, most people who saw the movie saw it in theater (the scene was not included to keep the movie from having a R rated...something I STILL don't understand since there is nothing naughty about the scene)
...did people hate Scott Pilgrim Versus the World? It doesn't have a great imdb/metacritic score so I'll include it because it's one of my favorite movies ever. Hilarious and incredibly entertaining.