The first Mortal Kombat had the most impact, I think, because most fighters at the time were trying to be the next Street Fighter, and then this new title comes along with an Enter the Dragon-esque atmosphere, and a level of violence never before seen in a game and blows them all away. IMO that was what rocketed the series to the top the fastest.

Ditto.

MK1 did it.

Every one liked MK1 so they made MK2, Which didn't ruin the series. Basically MK1 did it.

I remember a tiny video rental store where my family would go to rent stuff. They had video games and systems. I rented Genesis + a couple of games from there once.

One time I was there, and the guy behind the counter was upset. He started talking to my mom about this new game that was coming out that had violence and spines ripping out and tons of blood and how he thought it was terrible. He said it was so bad it was being censored. That was MK1 in a nutshell. It shook people.

teh spine rip

i think MK2 or MK3

I think it was a lot of things.
The digitized actors, the ominous atmosphere, the over-the-top blood and gore that hadn't been seen in any other fighting game at the time, easy to get into gameplay, and a storyline that only got bigger and more epic with each game.

The "Holy Shit i can't belive how bloody this game is" factor, along with the digitization and the simplicity of the fighting.

When they went to 3-d they lost som cred, because lets face it MK4 sucked big time. so they sort of rediemed themselves (in my eyes) when they made MK: DA. And although MK: D was slightly bad because of the story, they had redeiming factors, such as puzzle Kombat and the revamped Konquest mode. And the newest game MK "Armagedon" which is gonna be the "last in the series", which i highly doubt, will have the new Konquest mode and bring back infamous Charecters. Therefore, this step might bring them back to were they once were popularity wise.

which brings me to my closing statement, it is so popular because it was contravesial and simplistic.
my rant is over now, you can get on with your lives

in mk1 the fatalts mk 2 the blood mk3 anmtltis and brutalty

Definitely MKII. The graphics and sounds and hidden things made the game the most popular by MK fans.

mk11