no VF game has ever sold good
Actually they have. Saturn VF2 and PS2 VF4 original managed to sell over 1 million units. DC VF3 sold poorly due to the game being 2 years old at the time, and the featureless home conversion didn' t help matters either.
Making VF5 a 360 exclusive would be a huge mistake for SEGA. The game is only popular with the hardcore audience in the west which make up just a small percentage of the industry today. Secondly, VF alone can no longer sell a console in which the Japanese have little interest, and much less support for.
The fact is most hardcore gamers in both Japan and in the west are waiting for PS3 as it would seem at the moment that' s the machine which will gain the most support. Just like PS2 had with Tekken, Vampire Night, King Of Fighters, XenoSaga, Star Ocean, Time Crisis, Guilty Gear, etc.
The only exception was Sega' s early Xbox exclusives like Panzer Dragoon Orta and JSRF, which although excellent were still not enough to convince gamers in Japan that the XB was the one to get.
I would rather VF5 have more guaranteed success on PS3 rather than dissapointing sales which SEGA cannot afford to have on such a high profile title.