I'm going to say 1991. The debut of both Street Fighter 2: The World Warrior in arcades, and the release of the SNES in North America. Incredible year for gaming. Pretty much all the other years were excellent as well, but those two events stand out to me.
It's funny, today I still play SF2:WW, but rarely play SNES. I'm more of a SEGA guy, but I do play a fair amount of Switch these days... Just seems to me the SNES sound chip bothers me in a lot of games. Sounds fake and ghey.
1991 was not the greatest year for SNK. I probably played Sengoku the most on Neo Geo that year, but likely spent more quarters on The Simpsons arcade beat-em-up.