Plenty of PS3 games that have been released that has pushed the hardware limit.
Heavy Rain easily comes first to mind.
The Engine of Final Fantasy XIII and XIII-2 push the GPU and CPU chip hard.
Skyrim, Arkham City, MGS4 (Rendered cutscenes at 1080p), and so on.
There is plenty.
I think you have this impression that the PS3 is equivalent to a high end PC.
Which it isn't.
Skyrim pushed the hardware hard, in many ways.
As did FFXIII, you have to remember most of the game was rendered at 1080p that is serious usage of GPU and CPU.
But Heavy Rain is right up there, they had to deal with at times individual AIs in certain parts of the game. The Rendering done also with full AA was massive, as was the facial tech.
You have to remember that there was one Cell CPU with 8 SPE's, 1 disabled as it wouldn't work with all 8, 6 for devs/games and 1 for the OS. And not only that the console only had 256MB XDR and 256MB GDDR3 for the GPU.
Very minimal compared to todays PCs.