ooo free copys of doom 3....
yes there should be seperate versions because its not just graphics that will be held back by the ps2 port, it will be lenth of the game (i dont think anyone would like to keep swaping dvd's in the ps2),
a dedicated pc version would allow for:
more complex missions,
more controlls and useable items like bridge controlls without the pink rings of vc,
better quality models (atm i dont think they re-model them for the port)
multiplayer built from the ground up, i dont think ps2 will ever get multi player gta but if there was a dedicated pc version rather than ports then mabee it would finally be implimeted in a retail version,
downloadable / buyable expansion packs from rockstar rather than 3rd part modders,
it would make the game complitly different but console is still going to be good,