IIRC, you are right that the PS2 runs at roughly 300mhz, but you are wrong in saying that that means it is like a P2. It's a completely different structure and utilizes multiple processors, I/O chips, and GPU's. You can't just comapre 300mhz to 300mhz in this case.
As for the PS3, I do not recall what speed the new Cell chip is running at, but it again is nothing like a standard desktop PC CPU. It will again utilize multiple processors and chips, and reportedly be able to draw extra processing power from other Cell chips, thus making its real "speed" dependent on outside sources as well as just what's in the box.
Google "emotion engine" for PS2 specs, and "PS3 Cell" for PS3 info. There's a lot of info out there, and you'll see they are definitely not run of the mill Pentiums.