Just like my only reason for buying a GameCube was originally for Super Smash Bros Melee.
Obviously exclusives play their part - but once you've got the consoles, what does it matter who has the exclusives?
Exclusives don't make a console better. They give an incentive to buy a console, but don't improve the console itself.
I like my Xbox just as much as my Gamecube. I couldn't care less what exclusives are on which.