Most PCs do have a helluva lot more power than a PS2... but the PS2 doesn't have near the amount of overhead a PC has. Windows, device drivers, joysticks, keyboards, mice, etc... while PS2 just has a little controller and no operating system. (well it does in a sense... but then it doesn't.. it's really just there to tell the system how to run the games, play music or play DVDs)
That and consoles are designed purely to run games while PCs are designed to be workstations... true, they are becomming more and more like dedicated gaming stations- but they aren't optimized to do it... then on top of that, PCs have a wide range of peripherals which need to be supported for the game to run... and I think PS2 uses a different language than the PC.
So, in the end- games designed for consoles will run way better on consoles and games designed for PCs will run way better on PCs and much crappier on consoles.
It's like porting stuff from the Mac to the PC... errr wait that don't happen... it's like porting stuff from the PC to the Mac.
-SW