I'm Getting a PS3... Name 5 Must Have Games

[pearljammer]

Pixel Junk Monsters - best $10 you could spend on the PS3
Uncharted - what Zucas said
Ratchet and Clank - Fun game, not great but certainly worth it for $40 or less
MGS4 - If you're at all curious, get it. It's worth it.
Save your money and buy Disgaea 3 in August for your 5th game