Who would you like to see?
I have so many I want to see, but trying to be as realistic as I can, my list is (going 28 because the current MK game has 28 standard characters excluding dlc)
Superman, Batman, Wonder Woman, Aquaman, Green Lantern (Hal Jordan), Flash (Barry Allen), Martian Manhuter, Green Arrow, Black Canary, Hawkman, Vixen, Black Lightning, Doctor Light, Captain Atom, Captain Marvel
Darkseid, Lex Luthor, Bane, Catwoman, Black Manta, Star Sapphire, Solomon Grundy, Vandal Savage, Cheshire (Jade), Black Adam, Killer Frost, Red Hood, Circe
Obviously I want more, but trying to consider who's popular and or currently relevant.
...and Zatanna, have to have Zatanna lol