Honestly, hard to choose 1 (also, be surprised about what games came out in 2010 or 11 people forgot about because this gen started in 2013).
Mass Effect 2 - Great Combat, good story and was great to do different playthroughs.
Dragon Age Inquisition - People moan but I loved this, while some bits were to be desired (hate Solas with a passion), I've played it so much over and over, never done a Dwarf run though, ever.
Bloodborne - Just because it's awesome, played it through loads, never did a game + or bought the DLC though.
Horizon: Zero Dawn - I didn't know what to expect but when I got into it I was amazed at how good it actually was, the gameplay is great, story great and it's dang fun to play.
Weird to think FF13 came out in 2010 and I haven't played a new FF game since. That's just sad.