Morrowind. It's been a while since I last played but I've spent a scary amount of time on this game with dozens of different characters. One minute it would be 11:00pm, got another hour or so to play, great, the next thing I know the sun is coming up. Time really just flies when you play Morrowind. Still never completed it though...

Although Oblivion is good it just doesn't have the same feeling that Morrowind had, haven't spent anywhere near as much time on it. Funnily enough I actually completed Oblivion though.

Dark Elves and House Telvanni FTW!