There are some movies I liked that I wasn't expecting to be any good because they were just torn apart by critics. Good luck finding a single critic who has anything nice to say about Dracula 2000. Not that I think it's a masterpiece or anything, but I found it to be a solid horror flick with a pretty brilliant twist ending that it never got any credit for. I also wasn't expecting anything good at all when I watched The Cry of the Owl, which has a 14% rating on Rotten Tomatoes. I loved it.
I wasn't very excited when I learned that Guy Ritchie would be making Sherlock Holmes: Action Hero, but both of his Holmes films turned out far better than I expected. There are several other Holmes films that I enjoyed despite low expectations because of the awful reviews that they got, particularly the 2002 version of The Hound of the Baskervilles.
You can add The Thing to this list. The 1982 film is my second favorite movie, and I wasn't expecting much from the new prequel. It was from a first-time director, filled with CGI, and it got terrible reviews. I loved it. Also, I know I'm in the minority, but I enjoyed Alien vs. Predator a bit. Not enough to want to own the DVD or anything, but after reading tons of very harsh reviews, I was surprised when I found it to be a decent enough movie.