My vote is for Fury Road. I say this self-admittedly having seen none of the rest of the films, so please take that with the healthy dollop of salt it deserves.
Still, Fury Road was in my view Hollywood at its finest: A challenging film that is an emotional rollercoaster. I think it takes far more creativity and craft to make that than to make a number of movies about various real-world events, the various Oscar bait films. If I had seen The Martian, I might view that as another fine candidate, but I think that Fury Road was incredibly creative storytelling.
Edit: I ultimately saw Room as well. Room is incredibly good, but it's difficult to compare it to Fury Road because, despite some oddly similar themes centering around sexual assault and sex slavery, they're very different movies. Fury Road is a movie that is fun to watch. Room makes your skin crawl, but that's sort of the point: it's exploring a subject that is viscerally ugly, disturbing, brutal and tragic. I think Fury Road might ultimately be my preferred movie, but I can't say it's objectively better or worse than Room, which sort of indicates the stupidity of the Academy Awards: art isn't one-size-fits-all.