I may also included some games that didn't come out in 2015, but they're games I played in 2015.
Also I've had less time and less interest in video games in the past 2-3 years. I tend to only go after games that really interest me, and even though I might be seen buying a lot of games like other people, I tend to play them for not too long. So while there are a handful more 2015 games I played in 2015, such as Shin Megami Tensei: Devil Surivor 2: Record Breaker on my 3DS, I don't feel comfortable putting it on this list as I had only played a couple of hours of it.
So the top-ten list isn't really a top-ten list. Only The Witcher 3, MGSV, and Bloodborne are games that I went "Oh man, these are awesome", all the rest are games I dug.
I didn't play Fallout 4, Destiny, Batman, or anything obvious like that.
Did play Undertale but was greatly annoyed by the combat and didn't like the story that much, character design was charming and the music was very solid, though.