No non-Nintendo exclusive has made the kind of money that multi-platforms have. Not even close. There have been a lot of mediocre multiplatform games that have outsold MGS4, so I don't see how you can say it sold better as an exclusive.
Anyone can guess. It takes no effort to throw out lots of predictions and have some of them be correct. You are not and wiser or better for having your guesses be right. Even a blind man can hit the bullseye.







