The truly distinguishing PS3 features are its Blu-Ray drive and most importantly the Cell processor, which according to for example IBM is mulitple times faster. IBM is the maker of both processors, so I think IBM is the most reliable source on this matter.
To use the performance advantage of the Cell processor traditional game engines need to be redesigned, this will not or at least has not happened with regard to multi-platform games. IMO Motorstorm provides a good preview of the PS3's graphical, complexitity and general performance, though it's a PS3 exclusive.
Having said this even by using just the PPE togtether with the RSX the PS3 is very powerful. For example Genji2 looks great and performs well without even using the PS3's SPEs. Multi-platforms games which don't make (much?) use of the SPEs and have been ported from the XBox 360 like Final Night Round 3, Oblivion, Ridge Racer, etc are overall improved compared to the original, so even without tapping into the bulk of the PS3's power the PS3 can keep up.
IMO to judge the PS3's true power judge future exclusives like Lair, Killzone, Rachet & Clank, etc, not the ports. Remember that initially Atari ST games ported to the Amiga were either on par or slightly inferior compared to the original, but after a few years when the developers tapped into the power of its custom chips it became clear the Amiga was overall by far more powerful.
