[T-R]

I'm under the impression that each Virtual Console download includes an instance of an emulator. If that's the case, they may tweak the emulator for compatibility with each game (or hack the game itself). If you want to look into it some more, the guys who do 'Virtual Console WAD injection' might have an idea. ROM Hacking and (NES/SNES) console development sites/forums might have some information, too.

I vaguely remember hearing of instances where games weren't emulated accurately (or even as well as on other emulators), particularly with regard to slowdown on PAL consoles.

[ericd]

Yeah, in the one case where I tried the wii virtual console with a game that was big in my childhood (Contra 3), it just doesn't feel quite the same. Noone's gotten an SNES controller quite right, either. So I hang on to a SNES to bring out every now and then.

[JoshTriplett]

http://www.retrousb.com/ has adapters to connect the original NES or SNES pads to either USB or a Gamecube/Wii. I've used their SNES-to-USB adapter and it works perfectly.

[ericd]

Oh awesome, thanks! I'm gonna pick one up just for zsnes...