SuperGrafx came out in November 1989 in Japan. It was supposed to be the PC-Engine 2, with a 16-Bit CPU, much better graphics and audio.
Sadly, the SGX was only a modest improvement in graphics over the old PC-Engine/TG-16. No 16-Bit CPU, no improved audio.
Developers were happy with the old PC-Engine and stuck by it.
Only 5 SGX-exclusive games were made for it: Battle Ace, Granzort, Ghouls n' Ghosts, Aldynes and 1941. There were many powerful rumors about
a SGX Strider, but it never happened.
SuperGrafx is considered a collectors item,