The Wii doesn't have the longetivity that the PS2 had , Nitnendo pretty much threw all the best first title games in the Wii's first two years Zelda , Galaxy , Wii Fit , Sport , SSBB ,Metroid Prime etc etc , not to say that these titles are bad but in order to the Wii to maintain the momentum it's had , 1st party titles have been released left right and centre.
Unless Nitnendo can manage to sell Super Mario Desert and Super Mario Bathroom adventure for the next 6 years it couldn't possibly outsell the PS2.










