I'm going with Oblivion because certain things about Fallout 3 annoyed me, particularly when I'd go in a vault or subway tunnel for a quest, complete it, then get lost on the way out. Oblivion made it nice and just stuck a door in the final room of the quest. Oh, and Shivering Isles is awesome! Though I will admit it makes no sense how you can be the head of all four guilds at the same time, particularly when, if you complete the mages guild questline before the thieves guild, there's a major plothole (I just uncovered it this week) where you end up having to steal a staff from yourself.
themanwithnoname's law: As an America's sales or NPD thread grows longer, the probabilty of the comment "America = World" [sarcasticly] being made approaches 1.
