I'm not completely obsessive when it comes to 100% completing games, but I certainly tend to focus on side quests, map completion and collectables more than most people I know. In games with separate levels and especially if they tell you which side quests and/or collectables you've missed, I tend to be far worse. WIth something like The Elder Scrolls, it's impossible to do everything and I can accept that just fine, but I'll still flesh out my maps of every area as much as possible.