The 'Lost Levels' both on GBC and the SNES are not the full game. The SNES one was the closest but lacks something I forget, and the GBC game lacks the entire 9th world and a few other bits and pieces. The one on the WII though is the NES/FDS rom though so it's legit.

The thing I have is a custom(bootleg) cart of the original FDS game in .NES format burnt to a NES chip and soldered into a cart where the original readable chip was blanked.