True... but apparently there are "canonical" storylines/endings for some of the games (which have Liu Kang beating Shao Kahn at least once from what I remember.) Even if Shao Kahn is vastly more powerful than most of the other characters, from what I can find on wiki articles and such, most of that power is derived from black magic. Without that, while he's still very strong physically (in comparison to an ordinary person) just from the virtue of being huge and knowing how to fight, he's not so far beyond the other characters that nobody can even scratch him. And most of his magic seems to go toward stuff like weakening the boundaries between worlds, sucking out the souls of random citizens, and bringing people back as his undead servants... not so much in the way of direct combat abilities (most of his attacks are plain physical blows from what I've seen; some or all of his attacks might be magically-enhanced in some way, but he still mostly just punches, kicks, and smashes people with his hammer when he fights.)Mortal Kombat is a difficult comparison because it's a fighting game. Everybody has to be able to beat everybody else for game balance.
And as far as I can tell, it seems like most Mortal Kombat characters aren't that far beyond an ordinary real-life human, aside from fighting skill/experience and magic-related powers anyway. In terms of speed/power/durability they definitely don't get anywhere near Dragonball (and especially not DBZ) levels. In terms of power, they just don't seem to go that far beyond what a slight exaggeration of a very strong "normal" human martial artist can do--nobody's blowing up mountains or the moon or anything like that, though they might knock part of a wall down every now and then. On top of that, durability doesn't seem to go up with power as much as it does for DB/Z characters; nobody in MK ever takes an axe or gunshot to the head and just walks away with an "owwie" (...though you could argue that those don't count since Dragonball was still very "gag-y" at that point), and even when fighting-game character balance isn't an issue (like in the 1-player modes some of the newer games have) there are a lot of traps and such that kill you instantly. Speed doesn't go really far beyond normal either--nobody in MK goes around catching dozens of bullets effortlessly, or having entire fights in a single second too quickly for anyone around to see, or anything like that.
