I just always thought it was a bit anti climactic in Oblivion when I get an epic quest to go kill some vampire lord or ancient lich. I fight my way through the dungeons and their hordes of undead minions for a face to face confrontation with my opponent... Only to slay them effortlessly. These seemingly epic foes were barely stronger then their followers and I never really felt satisfied or challenged by any individual foe throughout all of Oblivion.
When I face off against a dragon or some ancient vampire lord; I want it feel epic and challenging. Not like I just killed some random no name bandit who has no real strength, power or intellect.