Which game will sell the most games: Halo:Reach or Gran Turismo 5 or FFXIII

[Munkeh111]

@ thx, so you think it will continue the decline that GT 4 started (though its total sales are still above Halo 3 btw). In the same way that GT 2 started a decline? What about the decline from Halo 3 to ODST?