How many of them are proper, accurate emulators though (and not emscriptened ones like mupen64)? Parsing bytes and mapping them to instructions is easy, and I believe that's why most of them are for very simple machines. We're still very far away from having multiple PS1/N64 era that are running at a tolerable framerate.

Except 1964js, which works in a way that both amazes me and makes me feel dirty at the same time.