Game Informer's website has a pretty big interview with series co-creator Ed Boon (creative director of NetherRealm) about Mortal Kombat. It has a lot of interesting questions, but it is broken up into like 6 small pages. Anyway, hit the link above or in the source for the full interview and here's a sample:
GI: How do you make everybody happy? You’ve got the instant-gratification people who want to print out the FAQ and do a fatality, and then you have the serious fighting-game players, too.
Boon: I think you need to make the average player able to do something cool and big on the screen. To throw a spear, it’s tap, tap, button. Ninety percent of the world can do that. Then a smaller percentage can do the quarter-circle fireball thing. And then a smaller percentage can interrupt the fireball and break out of it and do this. And then a smaller percentage can interrupt this, interrupt that. I think if you offer that for all of those levels, so this guy’s having fun because he’s throwing iceballs, and this guy’s having fun because he’s interrupting this move and cutting into this move and showing off in front of people, that’s where you get the big numbers in the millions of players.