Doom it's easy. Better the ZMachine with an interpreter based on DFrotz, or another port. Then a game can even run under a Game Boy.

For a similar case, check Eforth+Subleq. If this guy can emulate subleq CPU under a GPU (something like 5 lines under C for the implementation, the rest it's C headers and the file opening function), it can run Eforth and maybe Sokoban.