Sony Dabbled in 1st party exclusives on the PS2 and had some powerhouses, Gran Tourismo. Then when they PS3 came out they were forced to support themselves with them. They just didn't have the experience Nintendo had with First Party games. Ironically Sony really is a Hardware company even though they take losses on the hardware.
That said, you really can't argue that Sony's 1st party studios haven't turned out some quality and in some cases unique/interesting titles this generation. Nintendo would never have published a game like Heavy Rain, and it did well for Sony despite its issues. Then there's the Uncharted trilogy, the Resistance trilogy, the Killzone duo, the Ratchet & Clank Future "trilogy" (counting Quest for Booty), the LittleBigPlanet duo, God of War 3, the Infamous duo, the upcoming 4th Sly Cooper game, etc.
And yes, I know that Insomniac is now a multi-platform studio.
I may not care for some of those titles like LittleBigPlanet and God of War 3, but overall Sony's kept me pretty satisfied this generation when it comes to PS3 exclusives. It's just a shame that the albatross of the PS3's god-awful first few years still hangs over it like it does, because I think the console has long since redeemed itself.