To be fair, I heard those screens were from the PSP version when they were still making it for the PSP. Disgaea, or any of Nippon Ichi's games, was never about pushing the graphical envelope though.
Edit: I've been hearing some more stuff about the PS3 that bears looking into, such as the supposed awesomeness of Super Stardust, and the screens for White Knight Story look gorgeous & intriguing. I can't help but slowly gaining more interest in my large black box.