1. Scorpion: Most recognizable character in the MK universe, great backstory, greater moveset/fatalities, even greater impact in the franchise probably than any other character. PS: GET OVER HERE (the 1st special move that "changed" fighting games' history)
2. Sub-Zero: Same as Scorpion, second to him just because his "brother that took his name up" story plus the fact that in the original storyline HE WAS the offender puts him in the No.2 spot. PS: Iceblast --> 2nd special move that "changed" fighting games' history and the 1st finishing move that "offended" audiences!
3. Liu Kang: He beat Shang Tsung, Shao Kahn twice, Shinnok and who knows whom else before Midway decided that it takes two sorcerers (that previously had their ass kicked by Kang) to take him out that probably wouldn't be there if Kang didn't follow the "no kill" code. Oh, and he is a mortal! The fact that he is NOT a "cool ninja" (for little kids to be a fan of), he has NO cool catchphrases and the fact that he used to be just Bruce Lee's tribute character and even so made it THIS far, gives him the No.3 spot (if not higher). PS: If John Tobias was still in NRStudios' team, Kang would probably be No.2 or higher.
4. Shang Tsung: The sorcerer who cannot be trusted by anyone, not even the great and powerful emperor, the guy that took down the great Kung Lao and created the Outworld dynasty for 9 generations. The character that changes his appearance to whomever he wants, deceives and manipulates everyone, has created feuds with everyone (Kenshi, Kang, Shao Kahn, Quan Chi, Li Mei etc) and manages to survive... Now THAT'S a villain ! PS: Earthrealm inhabitant who betrays his realm gives him bonus cool points plus don't forget that Tagawa made him even cooler!
5: Shao Kahn: The ONE BIG BAD. Because he is both bad AND big! I don't know a lot about fighting games but to my eyes he cannot be compared to other bosses. HE OWNS. What's not cool about him? The deep voice & the fact he is the best fighting game announcer? The appearance? The fact he is unstoppable (except Kang of course!)? Just pure badass.
6: Raiden: Cool design! Lightning going through his whole body, the big straw hat, a tribute to the thunder demon from "Big Trouble In Little China" (anyone who said that any other character in this movie was cooler is a liar), teleports, cool gibberish crap while doing Superman moves, the god of thunder and protector of Earthrealm. Oh yes, I approve!
7: Kung Lao: Reincarnation of the original champion of MK, razor hat that slices up people in every way imaginable, one of the best set of fatalities and special moves we'll ever see (spin move from MK9 will probably give people nightmares till their 40's), runner up earthrealm badass next to "wua-tah".
Other important MK characters: Quan Chi, Kitana, Goro & Sektor .