It was tough to get my nominations but I believe I have the best six first party studios owned by Sony in this poll.
Incase some of you may not recognize the studios, heres a few games that each company made.
Polyphony Digital - The Gran Turismo series
Team ICO - ICO, Shadow of the Colossus
Naughty Dog - The Uncharted, Crash Bandicoot and Jak & Daxter series
Santa Monica Studio - The God of War series, Warhawk
Guerilla Games - The Killzone series
Incognito Entertainment - The Twisted Metal series, Warhawk