Right. That's why I didn't skip that generation in my example. My hunch was that as a general rule for those earlier generations that it's not possible to emula

Right. That's why I didn't skip that generation in my example. My hunch was that as a general rule for those earlier generations that it's not possible to emulate the immediately previous generation unless there was special support, but maybe you could go back 2 generations. This project being an exception. That's what lead to the Wii -> GameCube (similar hardware) -> [not N64] SNES -> NES (demonstrated by this project) example. Heck, if console manufacturers kept two separate branches "every other generation" emulation (odd/even generations) and then made sure each console generation had extra hardware to play the immediately prior generation's games (as some sometimes do), then every generation could play every other generation. That would be nice for players, but maybe not nice for the companies though.