The way to approach this problem isn't to write the emulator to run in the browser, but to build a remote client that controls the emulator running on a more po

The way to approach this problem isn't to write the emulator to run in the browser, but to build a remote client that controls the emulator running on a more powerful server. Not only do you get the benefit of the server's speed, but if multiple people are playing, you don't have to send machine state over TCP/IP, just graphics data. Gaikai and OnLive are doing this with current-gen games. Doing it with an SNES would probably be trivial. This does not, however, solve the issues of game compatibility that you mention in other comments, but in my experience the amount of games that don't work in SNES emulators is trivial.