A cult game? ... it's good, but not that good.
As far as the fighting goes it is vastly original when compared to the Street Fighter franchise and shameless knock-offs such as SNK's World Heroes. But even though it is original in its deliver, the whole package isn't really that good. For one thing each character is comprised of the same basic moves. Every character has the same "back, low kick" just as every character can preform an "uppercut." There is also not much diversity between characters. Sub-Zero, Reptile, and Scorpion all share the same character sprites with just a minutely change of color. It's the same case with Mileena and Kitana.
Even though pulling off fatalities is cool, in Mortal Kombat II they are near impossible to perform given the time frame to preform them, I heard that the time during the "Finish Him" mode as been lengthen on the home console versions, which is good, but I've only played the arcade port of the game and was extremely frustrated when trying to preform Scorpion's "high punch+hold, down, right, right, right, release high punch." There is just not enough time given in the arcade version to preform it. On top of this, fatalities can only be preformed at the end of the final battle (I guess to create a since of realism, but whatever... It's MORTAL KOMBAT!).
Anyway, to say though that this game is a flop is far from the truth, it still holds as a very entertaining experience, but as a classic?... That I'm not so sure about.