Where did you get this info? All the "early looks" at the game for magazines, reviewers, etc indicated the opposite...insofar as the early demos, etc were all shown on the 360 with a note saying the ps3 version would be identical.
Anyhow, this is about MGS4, not GTA4. MGS4 is a great game, no doubt, in fact it's one of the reasons i bought a PS3. My PS3 was getting a bit dusty
I'm not sure it has the "reach" of Halo though...Halo's main draw is online and it has some staying power there. MGS4's main draw is it's single player campaign, which skews more hardcore, as it's not a pick up and play sort of game, nor will it have the legs of Halo. Lets hope it sells a bunch of consoles and is followed up by more great games in the near future -- God of War 3 comes to mind, and for those of you that don't have a 360 or haven't played it, BioShock is awesome and coming later this year.
It's certainly a work of art, and IMO easily the best the PS3 has to offer thus far. Graphically it's beautiful, the story is engaging, and the acting good.