I bought it primarily for Jak 4 and Way of the Samuria 3, but I also knew that Sony would be cooking up some awesomeness with it's first party studios.
After I actually bought the system, I discovered God of War and Metal Gear Solid, and my purchase was validated all the moreo.
And while I haven't gotten Jak 4, and Way of the Samurai 3 is far from release in NA, I've been content so far. MGS4 was amazing, and Sony's first party has been cooking up awesomeness like Uncharted, just like I expected.
I also realized how much I loved Shadow of the Colossus this gen (despite having bought it and played it last gen) so I recently bought Ico, and now I can't wait to see what Team ICO is cooking up next!