Hard to decide, maybe Phantasy Star Online, but that's more for the people than the game. I love all the Final Fantasy games I've played (7 to 12, excluding 11), Borderlands, Morrowind/Oblivion/Skyrim and the Fable series
Seein' who's friends with whom and wonderin' why I can't make any friends. :( You all look like a fun bunch to hang with but, admittedly, I'm no fun. Guess that's it. Always admired your contributions. Take care.