This is THE decade for fighting games. There are lots of great games, but I would have to go with Street Fighter II (1991) and its variations. It may not be the best, but Street Fighter II was the one that started it all, and the true really legendary game here. I played Street Fighter II for the first time in 1991, and I had never seen something like it before. That was a game changer. Among all of them, I would have to go with the definitive version, Super Street Fighter II Turbo(1994) as my favorite in the whole decade. The other Capcom fighting games were also great, and I would have to mention at least the Darkstalkers (1994) series, and Marvel Super Heroes (1995).
Then there was Mortal Kombat (1992), with all its blood, and its sequel which I think it is even better, Mortal Kombat II (1993). Virtual Fighter (1993) was good, but not as good as Tekken (1994). The two best offerings from Namco would be Tekken 3 (1997) and Soul Calibur (1998), which are both really great. SNK games, although good, mostly paled in comparison to these offerings, but I think Samurai Showdown (1993) and The Last Blade (1997) series were among the best in the bunch.
Then there was Mortal Kombat (1992), with all its blood, and its sequel which I think it is even better, Mortal Kombat II (1993). Virtual Fighter (1993) was good, but not as good as Tekken (1994). The two best offerings from Namco would be Tekken 3 (1997) and Soul Calibur (1998), which are both really great. SNK games, although good, mostly paled in comparison to these offerings, but I think Samurai Showdown (1993) and The Last Blade (1997) series were among the best in the bunch.