Depends on what you define as "worth playing". I actually got the PS3 for Infamous. MGS4 is not a game you buy a console for. You play it at a friends house, shake your head and go home
But if you already have a PS3, buy it.
Other Games worth mentioning:
Demon's Souls, Valkyria Chronicles, Heavy Rain (Rent), GOW3, The Ratchet and Clank-games, Uncharted Series, 3d Dot Game Heroes, Maybe Little Big Planet and Folklore too aaaand that´s about all the Exclusives I own...stay the fuck away from Resistance, especially the first one, horrible game. Also didn´t like the oh so great Killzone 2...all very uninspired and boring to me...might get it now that it´s Platinum though...