I've seen PS to PC convertors so I'm sure a GC to PC one probably exists...

I know about the PS-PC converters, but haven't found one yet for a GC controller.

And yes, I do think the PS/2 controller is worse than the Xbox controller. I have several "issues" with the PS/2 controller. The Xbox is a mild improvement over the PS/2 but not by much. The only controller I've really genuinely liked (as opposed to "not disliking to an extreme degree") is the Gamecube controller.