There are rumours and counter-rumours over this. The only fact are that there's a lot of very well protected interests.
1. Pro Evo is an old Sony franchise now. However, it is licensed on GC in Japan. where its called Winning Eleven 6: Final Evolution. Outside of Japan Pro Evo is PS2 exclusive.
2. After the major coup of GTA onto Xbox (and Manhunt soon also) the big, BIG rumour is PES3 for the black doorstop with the ugly controllers. But the sources of these rumours are very vague, and seem to crop up in Xbox publications.
3. Konami subtley hinted at E3 that a PES3 beta for Xbox (a simple PC sideways port no doubt) is sitting in the wings. Waiting for the legal wrangling to be decided perhaps.......
4. PES3 is a system-selling game, as you admit yourself. Guess what, it sold a PS2 to me too. I doubt Sony are going to give this sensational game up lightly.
5. Konami are an old school company, they've always trodden a well worn path thru the arcades (aaah... "Track 'n Field") and the classic home platforms, with consistently quality titles. Its unlikely their going to rock the Sony boat.
PES3's biggest crime is not the cruddy commentary or the lack of proper licenses for the team names - it's the lack of online support. If PES3 had been equipped with quality online capability Sony could have made up substantial ground on Xbox Live.
Amazingly, FIFA2004 is online on PS2 but not on Xbox. This indicates strongly the legal power of Sony and the sway they hold over the major developers, thanks largely to their massive user base no doubt.
My opinion: PES3 will not come to Xbox in the near future, although Konami would love to see their cash cow wander over Microsoft's console. However, Sony's legal hold is immovable. But Sony should have made Konami put it online. It would have shifted another mountain of units and given Microsoft Xbox some Xmas indigestion.
SM
ps. The best version is the PC version? I play it on PS2 and havent seen the PC one. The PS2 game is untouchable - mankind doesnt deserve it. How good can the PC game be?!?!?!?!?!!!!!!