I voted Bloodborne for my top game but now I'm between Rainbow Six: Siege and Steins;Gate.
Rainbow Six would probably be my favorite online shooter if Overwatch didn't exist. Every match plays out differently and it's an incredibly rewarding and fun game to play. There are a million ways to approach every situation and it's just amazing. I wish I got into it sooner.
Steins;Gate has one of my favorite stories and I love the cast. Gripping game.
Looking at the list it appears that any I own from 2015 that is an original game (not remaster or port) has still been unplayed. So I have no answer for that year.
It's got to be Bloodborne. Incredible atmosphere, design and gameplay. Could sing it's praises all day long.
The Legend of Zelda: Majora's Mask 3D gets 2nd place, but doesn't deserve top spot being a remaster. Still an incredible game though, and the improved visuals and emphasised art styles really push it up.
The Talos Principle - Absolutely loved this game and the expansion. One late night I couldn't figure out a puzzle so I finally gave up and went to bed. I must have dreamed about the game because during the night I woke up with a eureka moment. I wasn't going to get up until I realized I suddenly knew the answer to two puzzles! Though I never did get all the stars...
Runner-ups include games that would be ok as my top game as well: MGSV (my original GOTY), Life is Strange, Tales from the Borderlands, Until Dawn
Between Life is Strange and Tales from the Borderlands, it really was a great year for episodic games. Their finales even came out on the same day, which was amazing.