I know, it's one of those threads.
But I'm asking because it doesn't seem so cut and dry.
In both games, there is a flaw.
In Oblivion, sound doesn't play a big role in being detected. You can shoot an arrow or spell right next to the enemy and he won't start searching for your character.
In Skyrim, lighting is irrelevant. The enemy won't have greater chances of detecting you when you're sneaking in broad daylight.