I agree with above, I've never even heard of the Mortal Kombat games merely surviving on gore. And, you know, about the storyline, I'd have to point out that MK storyline is pretty complex and fairly good, though, like most fighting games, it's somewhat hard to find out everything clearly without outside info (though much easier than Street Fighter).
Like all fighting games, it survives on it's playability. I've gone to the official MK forum, and, to my surprise, that's what most people there cared about, as well as the storyline. There were several debates about the different ways to view the game (though much less extreme than, say, here), but it was far from enough for me to get the idea that people only cared about gore (the ones who did were apparently very young, as well, though I'm only saying that from inference from other people on the forum).