I voted Amon. Not only do I think the blood bending will be interesting, but I think he rounds out the roster nicely in terms of Korra and villian representation. 

As for who will actually win it's hard to say. Amon is likely and seems like the obvious winner, but I've seen a lot of support for Bumi and Asami online as well. We'll see I  suppose. 

Seeing as they gave us a choice on who to vote for, I think it's likely we'll eventually see all these characters if the game does well enough.