In my opinion the three best performances of the year were Leo in Revanent, Matt Damon in the Martian, and Will Smith in Concussion.
@MartyMcFly has been making a case for Fassbender in Steve Jobs but I think those three narrowly beat him out. Of those three I am of course going to ride for black excellence first and foremost and champion Will, but he hasn't gotten the push or the buzz that's needed to carry him past Damon, let alone Leo. And between Leo and Damon I feel that Leo CLEARLY was the stronger performance (and this is no shade to Damon, who carried that film on his shoulders for damn near an hour and kept me engrossed) but Leo truly put his heart and soul into his Hugh Glass character.
This is his year, and I honestly don't think there is any doubt about it.