To people who don't understand Street Fighter and/or were too young at the time.
SFII' for PCE was released in Japan in June of 1993. SFII' is the second of five versions of Street Fighter II released in arcades in the early 90s. Three were CPS1 based, two were CPS2 based. Every incremental version of SFII was hugely important to fans of the game. I can't stress this enough. The two version with the most enduring fandom are Turbo (3rd game) and Super Turbo (fifth game). SFII's most distinguishing features were that you could play as the bosses and you could PVP the same character.
At first SFII (first game) was SFC exclusive. After this Capcom decided to diversify. They went to all three systems...sorta.
Street Fighter II was a hit for a few years straight. Updates were more or less annual or even more frequent. I don't have a full scheduled but I know that Street Fighter II' Champion Edition (full name) was released on PC Engine in June of 1993. Only a year and a half before the PlayStation and Saturn. The last days of the systems popularity. It was more expensive than even a SFC game and it required at least one brand new controller to play. Basically it required two since Street Fighter one player is f*cking pointless. If you didn't have a tap you'd need one of those too. Basically over $200 which was nearly enough to buy the PCB by then because Capcom had already released the next edition to arcades and that next edition, SFII'Turbo: Hyper Fighting was scheduled to be released ONE MONTH LATER on SFC.
That's right. While PCE was the only way to play SFII'Chapionship edition at home before 32 bit ports (if you mention Genesis, you are wrong, go away) but it's freshness date passed only one month later when a LESS EXPENSIVE version of Hyper, the NEW GAME, came home.
The reason why they didn't release it in the US is because it would not have sold. Americans are cheap. If they were crazy like me and actually have a Duo they probably still didn't want to blow $100 on an out of date game and TTI, who had banked everything on the merits of CDROM2 probably didn't want to have to explain why SFII, the most popular game in the world by then, could only be done on a HuCARD that cost way more than any other HuCARD. It didn't even sell well in Japan from what I can tell based on the game being hugely discounted very quickly.