Well, from what I hear the GC disc is non-standard. My DVD drive on my PC doesn't even know that there's a disc in there, so I'm inclined to believe that Nintendo has done something to the disc.
The PS2, on the other hand, uses DVD's. With the exception of the protection (which nobody has ever actually pinned down) "track", it's just an ordinary DVD.
XBox DVD's are "encrypted", but they are still ordinary DVD's.
But it's VERY hard to crack a protection for a game that you can't even read.
- Gurm