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
Thank-you, and you are welcome. Spent the day playing Gears of War, oddly enough, but I will not be seeing any "suggestible young ladies" until tomorrow (Saturday)! ;)