Yes, I don't have any Classic controllers yet, just GCs, because Classic controllers can't play GC games, which is incredibly stupid.
Nintendo should make a new Classic controller that has analog triggers, then it would pretty much be compatible with GC games, even if it may not be as comfortable as GC controllers.
I guess maybe Classics wouldn't work because there needs to be GC controllers plugged into the GC ports? I don't know.
There are 3rd party "GC" controllers that are pretty much Classic controllers though, such as this: http://gear.ign.com/articles/819/819888p1.html
May not be very pretty, and perhaps the controls won't be as tight, but it is laid out better for some.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )
