Why are people so upset over this?
Shouldn't we be happy that more people will be able to enjoy this highly anticipated game?
The 360 has terrific video RAM, so graphically SE won't dumb down the game, and the 360 does well with multiple discs (without installation), so space wise the game won't be dumbed down. We can expect the full potential from this game on both systems.
So why the grudge?
Is everyone really so insecure about their PS3 purchase that they need everything to be just for them and the other systems must fail?
I own both systems, so this never really mattered to me, and I'm happy that more people will be able to enjoy the game now. It'll be good for the game makers and the players. I didn't hear any complaints when the news about Bioshock or Eternal Sonata (before the possible cancellation) were not going to be 360 exclusives.
Think of it this way, PS3 is not losing anything. It's just that more people can enjoy what's good. Why be upset about that? ...or did GTAIV seem less fun knowing that 360 owners are enjoying it too?