Funny thing is i have never brought a COD game for the PS3 and dont plan to. When i see people buying PS3's they get COD, GTA.

GT5 has not come out yet

That's one of the great things about the PlayStation 3, at least now.
The PlayStation has such a diverse round of excellent high quality exclusives that there really isn't anything that solely defines the platform. If you asked me, I'd say Resistance, Killzone, Metal Gear Solid, Ratchet and Clank, Gran Turismo and Final Fantasy are good reasons to buy the platform, but there are many others.

Metal Gear Solid: Rising is a spin off game, and as such does not deter the game from having a sony brand image, we all know it still does. When you get MGS4, that's the time when it changes.

GTA IV is by and away in the lead as far as PS3 titles go, so I would say that game. It's former association with the Playstation brand probably helps it to be a must buy opening title for prospective PS3 owners.

first game that i bought was heavenly sword.

I got mine with MotorStorm and Folklore.

Quite odd but w/e. MS was heavly bundled at the time so...

And Folklore was the First AJRPG for PS3 so...

Ya...

As for the common new PS3 buyer in 09, i'd say Valkyria, LBP or KZ2. all exclusives.

I bought Ninja Geiden Sigma when i got it since there wasnt much else at the time. I got Rainbow Six Vegas afterward which got me totally hooked on FPS's....