There were somewhere in the vicinity of 10 billion PS2 owners...having the breadth of exclusives that Sony offered was necessary when you controlled 90% of the market. They had a large user base with varied tastes to support.
The PS3 does not enjoy the same market dominance and therefore does not have the user base to support the wide variety of games they offer at the levels you suggest. It has less to do with marketing than simple logistics.
That being said, the cream usually rises to the top, ergo the large sales numbers of the Uncharted and God of War series.








