An online service that is simply the best on consoles.
More games than any other console this gen.
An excellent array of exclusive retail games dating back to 2005 (games in its first year included the excellent PGR3, Crackdown, Dead Rising, Saints Row & Gears of War, thus there is a HUGE back catalogue of games there to catch up on).
Don't get me started on XBLA, its been nothing short of exceptional from day 1, overall it blows the competition out of the water.