Mortal Kombat 1 & 2
I have to cover MK 1 & 2 because covering just MK1 simply wasn't enough, If Street fighter set a new standard for fighting games MK took that standard and violently raised it
Now, before MK there were fighting games were you could kill your opponents, for example
Time killers
In this game you could chop up your opponents to bits and this game was around the same time MK first came out but MK1 brilliantly set a more gruesome and realistic tone simply by using digitized graphics of real actors instead of using animation.
I kidd you not, when MK1 first came out and kids saw this
we flipped the f*ck out, and when parents saw it they flipped out too and gave MK the first ever
MA rating in a videogame