Holy moly! I've posted this poll in 3 places: reddit, here on TYM and on gamefaqs. The results are so tight that it's a lot like a savage showdown for who will rule from the Outworld throne!
So far, here on TYM we have:
Shao Kahn with 20%
Kotal Kahn and Mileena both with 16.7%
Rain with 13.3%
Kitana with 10%
Even Reiko with 7.6% would still have chances
But reddit is the place that brought the most voters (about 100 in just a few hours):
https://strawpoll.com/xd288wb6
Kotal Kahn has 16 votes
Kitana has 14
Rain and Skarlet have 12
Mileena has 11
Shao Kahn has 9
Reiko or the shokans have 7 each
Daegon has 5
Ferra/Torr doesn't seem to be taken seriously, has just 2 votes, long way from the others
And on gamefaqs, after about 65 votes:
https://gamefaqs.gamespot.com/boards/253573-mortal-kombat-11/77417655
Mileena has 17
Shao Kahn has 14
Kotal Kahn has 12
Kitana has 8
Rain, Reiko or a shokan have 4 each
Surprisingly, Skarlet, who has 12 votes on reddit has only 1 vote here.
Daegon also has 1 vote.
Ferra/Torr is not taken seriously it seems again.
Adding all the votes up, it seems like it's a very tight fight between Mileena, Kotal Kahn, Shao Kahn, Rain, Kitana and even Reiko and Skarlet.
I'd really like to see such a fight and schemeing in the game. They could make MK the next Game of Thrones if they focused on Outworld more.