The only person who still considers the quest for the Iron Throne a "game" that can be "won" is Cersei, who is clearly off her rocker. Daenerys seems the obvious choice — but obvious is boring and "Thrones" is never boring, so I'm going to guess that Dany will somehow be sacrificed (though, God help me, it better not be happily in childbirth, or I will set fire to the Seven Kingdoms myself).
Which leaves Sansa. No one has more clearly seen, up close and personal, the perils and benefits of power. Her early narcissism and naked desire to be queen is worrisome, but she has changed more than any other character in the story, save Bran, who literally isn't himself any more.
Sansa is still very much herself — the oldest daughter of a noble house who has survived, as heroes must, all manner of suffering, without surrendering her humanity. She has become a fine strategist; thanks to Cersei and Littlefinger, she understands the necessity of ruthlessness, and, thanks to Jon, the importance of mercy in victory. She is still human enough to love (I nurse a secret hope that she and Tyrion get together) but is no longer ruled by her emotions or personal desires.
The whole point of "Game of Thrones" is that it is not a game, that the masses sacrificed to the hubris of kings will rise and demand a reckoning. The real weakness is not honor but false pride, the desire for legacy or dynasty or vengeance for its own sake. There is a difference between wearing a crown and ruling a nation.
Jon, and even Daenerys, may understand that, but they are, essentially, rulers in war; only Sansa makes sense as a ruler in peace.