I have to be honest... Literally none
Been a fan of MK since the original came out and over the years I bought the odd beat 'em up here and there because I figured there must be something I love about them as a genre; I had Weaponlord (SNES), Street Fighter 2 Turbo (SNES), Tekken 2 (PS1), Cardinal Syn (PS1), Soul Calibur (Dreamcast), among a few others - typically either something ultra-violent or apparently genre-defining as a fighting game, but none ever connected with me other than Mortal Kombat.
Like former MK-media mogul Lawrence Kasanoff once described MK as being "Enter the Dragon meets Star Wars", it too hit that little special world for me that mixed something anciently Asian and mystical with something unique and weird with a sci-fi edge all tied up in an ultra violent package as the cherry on top.
I quite literally love "Mortal Kombat" alone for its universe and lore (and am acutely aware of both its ups and very
very low downs) as well as its grotesque violence, and really am not much of a beat 'em up fan as a genre.
It's why I'm still absolute shit at MK11 and won't play any of you online haha... I concede I don't understand the mechanics of a fighting game or how to master it, I literally can't understand 'frame data' or how on earth my rubbish brain can be expected to notice it. I just love to see what happens to these crazy characters and this universe in every instalment and the new wonderful ways to viscerally murder one another each time (and as an added bonus in MK11 specifically; sit around dressing up the characters as I'd love them to look - you have no idea how much I love character customisation in games, least of all for characters I've been a fan of for over 25 years!).
Guess it's why I don't care for the guest characters in the slightest, to me they're not meant to be part of that world that I love. I'm the dopey geeky idiot who tuned in religiously to watch Conquest, Defenders of the Realm and Legacy each week to see what happens to the incredibly loose and ill-defined story canon rather than study the move-sets and variations for Geras on how to rise to the top of the Kombat League haha.
But hey, that's just me!