The Witcher 3 and GTAV are both very good games. Best games since Skyrim (2011), imho. Take your pick. If you enjoy fighting monsters, pick TW3, if you enjoy driving cars and hitting pedestrians in the teeth, pick GTAV. Or just play both. GTAV gets less press these days, because the PS3/Xbox versions were released years ago. Hype requires freshness. But if you haven't play GTAV on a console, it's definitely fresh to play it on a PC now.
2015 isn't over yet. We might get a few more good games. I suspect Fallout4 is gonna be good. Personally I have my eyes set on Tangiers (to be released in November).
Dying Light was released January this year. I was pleasantly surprised. Simple concept, good execution. The story was average. The graphics were good. The movement, parkours, was just awesome.