The problem is, even those crappy integrated GPU's are 10x as fast as those found in PocketPC's. Take a 400mhz PC, run a N64 emulator, and set it to software rendering mode, thats the speed you will get on most PocketPCs if your lucky.
Not to mention, assuming you get 100% speed and sound, imagin trying to pretend that your pocketpc's buttons are an N64 controler, emulating 2 shoulder buttons, 4 camera buttons, a 4 directional D pad, an analog stick, A and B buttons, a Z and Start button. How fun....