Don't buy LittleBigPlanet.
Don't get me wrong, 'tis unarguably one of the best games on the system. But the sequel will be released almost immediately after Christmas, and by the looks of it, will be vastly superior to the original.
I've got no idea what kinds of games he likes, but if I were him, I'd want to get one of these games as a present:
Bioshock
Street Fighter IV
Red Dead Redemption
Uncharted 2: Among Thieves
Batman: Arkham Asylum
Assassin's Creed II
or Metal Gear Solid 4: Guns of the Patriots. (But I think you mentioned, that he has already played & completed that one.)