I'd just like to point out that nobody has mentioned Grand Theft Auto 4 will be out for the PS3 soon enough (and judging by screenshots of the PS3 and Xbox 360 versions, the PS3 version looks decidedly juicier at this time).
And it can be said that Grand Theft Auto 3, Vice City and MGS 2 arguably (along with Gran Turismo possibly) made the PS2. I'm thinking GTA 4 will shift it in favour of the PS3 as GTA: Vice City did for its predecessor.