It seems that after I unleashed that CHIP-8 emulator for #emacs someone else felt pressured to unveil their Gameboy emulator: https://github.com/vreeze/eboy
After some tweaking to get the code to byte-compile, I've made it run at 1.6 FPS (author claims 1 FPS interpreted). Thanks to frameskip you can actually see things move. Here's a recording of Tetris in demo mode: