In the first couple games, you can easily see that all the characters were based on or an homage to something that Boon and Tobias liked, and one of those things was comic books.

Scorpion definitely owes a lot of his aesthetic to Ghost Rider. He also has a very similar backstory to Spawn.
Baraka was based heavily on Wolverine.
Kitana and Mileena probably owe their MK2 looks to the Daredevil character Elektra.
They've even mentioned before how similar Sub-Zero in MK3 looks to the X-Men character Cable.

Outside of comics...

Kano's faceplate was inspired by Terminator.
Johnny Cage is dressed like Jean Claude Van Damme from Bloodsport.
Liu Kang is obviously Bruce Lee and the plot of MK1 is just Enter the Dragon with magic added.
Raiden was inspired by a character from Big Trouble in Little China.
Kung Lao's hat comes from a James Bond villain.
They even revisited the idea of basing characters off kung fu movies in the later games. Kobra was inspired by a bad guy from Karate Kid, and Darrius' alternate costume was an homage to actor Jim Kelly.

and sonya is based on Cynthia Rothrock. And btw origionally this game was going to be the bloodsport game - but jean claude van damme declined to do it. So they worked on what they had to make a mini project. And that is how Mortal Kombat came to be. Probably best that things did happen like that otherwise we never would have had fun playing the series or reading the comics.

oh man, i thought it was only scorpion and liu kang that got based off other characters, seems like its practically everyone. but cool stuff to know.

yeah - well its things like this that confuse me - when people say how much they hate liu kang and how hes a complete rip off of bruce lee. It winds me up so much as it just proves they don't know jack shit about MK as a franchise and where its roots lie.

AANNDD:

Cyrax, Sektor,and Cyborg Smoke(MK3) resemble the Predator(Movie Series)
Blaze was based on the Fantastic four's Human Torch
Bo'Rai Cho is based on my fat uncle Joe (just kidding)

Oh yeah, I'd forgotten about the cyberninja dreadlocks. Usually when I think about their MK3 appearance, all I remember is that all their armor is dirtbike pads. Which reminds me, Kabal is based on the Tusken Raiders (sandpeople) from Star Wars.