Yeah, computers will have to become 20 times faster to be able to make GC emulation in its current state playable. [for complex games like Mario Sunshine that is] Still, that's not going to be _that_ long given how quickly PC's are getting faster. Either that or they become heavily optimized and run on one 10 times faster, only time will tell.
Cheaper just to buy a GC at this point, if you want it through your monitor that badly buy a TV card.