god damn COD 4 would be great as a co-op game, because lets admit, when its just you and a friend playing one-on-one, you get bored fast and just start taking it in turns on xbox live.
yeh uh fable II had co-op, it was just the GTA style of don't-run-too-far-from-me-buddy co-op which gave you the s**ts when you wanted to shoot at some baddies from a distance while ur friend attacked with a sword.
The list should definitely included the new-ish Prince of Persia. You play through the whole game with two people, why couldn't you have online co-op???