Console A is capable of selling 60 million.
Console B is capable of selling 100 million.
A full GTA exclusivity on console A may enable it to beat console B.
It depends on the natural sales gap between console A and B. If the gap is small, then the additional exclusivity of a single 15 million+ selling title will decide the winner. If it's big, then something like a GTA exclusivity will be needed.
But releasing a major exclusive early in the gen can have a profound domino effect. It helps make the console the go to platform for most games and invites more exclusives.








