If the SGX games had been made for one of the other popular (and comparable) systems around at the time, they would still be regarded as good games. Particularly Daimakaimura, Aldynes and 1941. Regardless of the system, they were great games for their times.
If you move the PC-FX library to the Saturn or Playstation, however, the stuff just gets buried. Zeroigar and Zenki, as well as the better anime games, would be considered 2nd rate compared to the real heavyweights.
EDIT: In response to some of the above, I think the best way of looking it is to see that there is no way that the SGX would have been successful. Maybe if a miracle happened and the best game ever came out on it, it would have sold. With any less ideal conditions, though, it was doomed.
The PC-FX, on the other hand, had much more of a chance. Sure, they flubbed the hardware design, but even so, all they needed was a few really solid and distinctly next-gen games in 1995. Preferably including at least one great action game. It might not have lead the pack, but it wouldn't have sank like it did.