Not always, Insomniac and From Software are major examples of that.
I don't get the idea that Sony's internal output on PS3 was leagues above PS2 in terms of quantity, I mean, Ape Escape 2-3, Ico, Shadow of the Colossus, Siren 1-2, God of War 1-2, Jak and Daxter 1-3 plus X, Syphon Filter: The Omega Strain, The Mark of Kri, Primal, Ghosthunter, The Getaway 1-2, Wipeout Fusion and Gran Turismo 3-4 don't count?