It wasn't because of the controller that few developers made games for the GC; it was the optical disk format they used.
To me this brings up an interesting point: how much dependance do you have to have in a console on cross-platform games, and how much SHOULD you be looking for exclusives? Obviously you need some of both, but how important to the sale of the console is each? We all know the impact Halo had on Xbox sales, but what about the other series, like the FF being on PS2, nintendo's "old standbys" being on theirs, etc? And how much did it help the xbox (or ps2, or GC) that MOST sports games came out for all 3 consoles, along with a great many other series of games?
That's something I don't see discussed much. Sometimes it's stated as a "foregone conclusion" that you NEED to have the cross-platform games on your console, but really do you, and by how much? And how much are the pure exclusives important?