The trouble with a computer game company telling the public that they have exclusive rights to certain games is that you are never told how long for. A game will be advertised as an exclusive title but the fact of the matter is that the tearms of the contract often reveal that the exclusivity is only available for a certain time. Once this time expires the company is then free to do what they will with their game and releasing it on other consoles means a shed load more money. Everything comes down to how much cash one developer is prepared to throw at another in the business and corporate world that runs it all.
Titles being "exclusive" to certain consoles and then coming out on rival consoles months later has been going on for years. A few examples of this. Nintendo were meant to have the licence and exclusivity rights to Star Wars a couple of years back, now you get Star Wars games on all consoles.
Sony had exclusive rights to the GTA franchise but months later, bam they are released on the X-Box. San Andreas will move to Microsoft before long.
Always remember that when you are told 'This is an exclusive title' you should reply with, 'That's nice... how long for'
The only true exclusive titles for any console are first party developed games.
Think about all those people that dont have a Gamecube aswell, for them it will be great news, now they dont have to buy a whole new console just to play a game they like. If it's a great game it deserves to be shared does it not?
I see where you are coming from though, Nintendo have be making a lot of grave mistakes in the past few years. Loosing Rareware

for example... need I say more. Dont worry though dudes. Nintendo will have something up theis sleeves to shut all their nay sayers up for a while, they always do.