GBA= should be possible and perhaps perfect speed
SNES=should be perfect
N64=not possible, unplayable slow, so waste of time
PSX=could be playable, there were emus for pc that were fullspeed on 300Mhz
Neogeo=should be playable, perhaps ram issues
X86=perhaps a 286 or 386, man that would be cool.
In general, we should be able to emulate almost every mame game, except those 3D ones and the HDD games.
Also we should not forget all those PC ports which should be possible! Like Exult, Quake (fullspeed), Duke 3D and so on.
PS: please add a touchscreen