The Force Unleashed would definitely be up there for me. It had a few bugs, and not much replay value, but it was definitely a lot of fun. I'd give it 8.2 at least.
Going back to the PS2, YuGiOh Duelists of the Roses was also a lot of fun. It wasn't very deep, but it wasn't bad by any stretch.
Lego Rock Raiders is also awesome, but I played that years ago.