League of Legends I guess. I was like meh I guess I will play it since it is free. Now I play it most days and have had great fun with it.
Last one would be Uncharted 2. The reason it blew me away is because I thought it was extremely overhyped and it kept getting number 1 in PS3 games. I played the demo and got annoyed at platforming and did not go much further then that. When I finally got the game one day and played through it, it blew me away at how great of a game it actually was.