If you watch enough G4TV, this should be no surprise to you. During the purple reign of the SNES, Nintendo of America maintained a strict censorship policy that limited the amount of violence in the games on its systems.
Then, like now, Nintendo was aiming to market a family console. When the notoriously gory Mortal Kombat began sweeping the gaming world, Nintendo refused to allow the level of violence that the game had on their system.
The blood and finishing moves were toned down, so that when players were hit, cut, or stabbed, they would just sweat profusely. Check out a comparison image between versions here.
Gamers really hated the censorship. The Sega Genesis version, wasn't censored and gamers flocked to it. That version outsold the SNES one by a ratio of 3 to 1! This made Nintendo reverse course and allow the developers to put in anything they wanted for the sequel.
If you know much of Mortal Kombat, you might be wondering why after the first game, Nintendo started allowing the violence. Well until that point, video games weren’t rated in the same way.
Mortal Kombat’s success was the trigger for the creation of the modern video game rating system in the US, and so Nintendo felt its censorship in that department was no longer needed.
As a result, Mortal Kombat II on the SNES outsold the ports on other systems. If there’s nothing else to take away from this, it’s that thanks to gratuitous violence, we now have a safe and reliable way of knowing which games are appropriate for different age groups.