Honestly, if you aren't using your Hogwarts house to make all of your life choices, are you really living? There are plenty of arbitrary and made-up "personality" types to make life choices based on, like astrology, but at least Hogwarts houses are simpler and are self-aware that they aren't real.
Fighting games are always difficult to pick a character to play with at the start because there are simply too many options and it can become overwhelming and coins with that many sides don't exist. Mortal Kombat features a large cast with tons of characters, so you can pick ones that matches your style.
10 Erron Black, Slytherin
The old west gunslinger Erron Black is a perfect choice for Slytherins because of his dedication to getting the job done and lack of regard for possible consequences. Erron Black is also not strictly a villain, just a man who gets hired for a job so that works for any Slytherin who can't commit themselves to villainy just yet. Erron Black plays dirty because he plays to win, which lines up pretty well with the devious snake house. If you ever have thought about bringing a gun to a fistfight, Erron Black is for you.
9 Cassie Cage, Gryffindor
While the attitude of many Mortal Kombat characters might make them lean away from the courageous house Gryffindor, Cassie Cage fits the bill, even with all her sass. The daughter of two expert fighters who can never stop talking, Cassie devotes her adulthood to helping Earthrealm forces fight off evil, which is definitely something a Gryffindor would do. Considering her Father's pedigree and probable riches, she certainly could have lived a spoiled life in Hollywood, only proving the point even more.
8 Sub-Zero, Hufflepuff
Sub-Zero does not have the levity that most Hufflepuff possess, but he is deeply driven by his emotional connections to others, putting him into Hufflepuff. While his constant quest for revenge may make him seem like a Slytherin, the fact that his goals ultimately shift to rebuilding his clan and him even becoming friendly with Scorpion in Mortal Kombat 11, makes it clear he cares more about others than vengeance.
Sub-Zero ultimately has a heart of gold, even if it drives him to just beat the sense out of every single person who looks at the Lin Kuei wrong.
7 Skarlet, Ravenclaw
This pick is relying heavily on the concept that blood magic takes a high intelligence to use, which may or may not be true. Skarlet is the only character ever seen using it so it's safe to assume its at least not easy. Skarlet relies heavily on magic and ability over brute strength, which lines up with the Ravenclaw ideology of being smarter than everyone else. Why punch somebody to death when you can stab them with your own blood right? Skarlet seems to have a strong grasp of how conflicts are going and strategically switches sides and exits whenever its most beneficial.
6 Johnny Cage, Slytherin
While the older Johnny Cage in Mortal Kombat X and Mortal Kombat 11 is a bit more mature, overall Johnny Cage is a selfish man who constantly screws over others to get what he wants. He is incredibly overconfident and egotistical, ultimately earning himself a place in the Slytherin house. Johnny does not contain the intellect or focus that some other Slytherins have but he certainly moves with purpose towards his goals. His self-centeredness and occasional cowardice keep him from even being considered for Gryffindor, which is the closest house to Slytherin.
5 Liu Kang, Gryffindor
Liu Kang over the many iterations of Mortal Kombat is typically the hero of Earthrealm, winning the tournament and becoming champion. In the most recent timeline of games, Kang continually tries his best to be the champion of Earthrealm but is beaten down by the forces around him.
Even though Kang ultimately ends up a revenant, the young Kang brought into the future is the one that saves everything. Kang is the hero consistently in Mortal Kombat and it is always for the good of Earthrealm and not himself, making him a member of Gryffindor.
4 Jade, Hufflepuff
Jade has a history of making bad choices, especially choosing to work for Shao Kahn, but her reasoning for doing so makes her a Hufflepuff. Jade is a childhood friend of Kitana's and ultimately just went with her wherever she went. When Kitana served Shao Kahn, so did Jade. When Kitana left Shao Kahn's rule, she left. Protecting others from execution in Mortal Kombat 11 further showcases that she has deep compassion for others, despite being an assassin.
3 Raiden, Ravenclaw
Raiden spends all of his time thinking, ultimately resulting in his own demise. During the most recent timeline of Mortal Kombat visions of the future drive him to try and alter the timeline in order to save others. Unfortunately, this results in him killing Liu Kang and eventually killing Shinnok, driving him to become evil Raiden. Despite the evil, every single action he makes is calculated and tactical, if not cold. Raiden is simply trying to create the ideal outcome, even at the cost of others. This way of thinking puts him in the Ravenclaw camp, leaning a bit towards Slytherin.
2 Frost, Slytherin
Frost is the overambitious and impatient apprentice, just like Anakin Skywalker. Her rage and inferiority to others causes her to take evil actions and act out against her master, Sub-Zero.
When Sub-Zero made peace with Scorpion, she lashed out and tried to usurp him, ultimately getting defeated. Her inability to forgive, coupled with a strong desire to obtain power and revenge makes her a full-blown evil Slytherin. Not every Slytherin is evil, but this one is.
1 Kotal Kahn, Gryffindor
Kotal has had a pretty rough life, being the last of his kind and having been experimented on by Shang Tsung, but he has a good heart. During his time as ruler of Outworld, Kotal stops the constant attempts to conquer other realms, instead choosing to focus on stabilizing the Outworld that is already there. He does his best to be a good leader, if not occasionally harsh. Kotal does have a good heart though and legitimately wants things to be better for people, making him a Gryffindor despite the occasional shortcomings.