I haven't played much, but Fallout 4 would certainly be on the first place even if I did. It's actually excellent candidate for 2016 too, at least untill Crowfall or Camelot unchained launch!?
Undertale took it for me. By far the most ingenious game simply due to the limited resources and how well everything was made using just that. Plus the music is fantastic (Megalovania, Battle Against A True Hero, Bonetrousle, Death by Glamour), and the characters are so wonderful you can't help but feel bad when you kill them in the Genocide Route.
I'm surprised no one has mentioned Shadow of Mordor, or Final Fantasy Type-0! That being said my top 5 list is 1) Final Fantasy Type-0 2) Middle Earth: Shadow of Mordor 3) Undertale 4) Life is Strange 5) Child of Light.