Damn, that's hard. I would say it's between Uncharted and LBP.
Uncharted's strengths: Fun to replay, again and again, phenomenal graphics, platinum trophy gives you something to aspire to (as it's possible for a normal person)
LittleBigPlanet's strengths: Amazing co-op, simple but deep, a wide variety of user created levels, graphics are almost as good as Uncharted, and the option to create your OWN level.
Between those...I'd have to give the edge to Uncharted, but only slightly.







