x-com 2 was fun - esp with the expansion which was (imho) quite good. I haven't played the other two so i can't contrast them also they are very different kind of games. I tend to view deus ex and prey as basically fps with advance play options while xcom 2 is pure strategy (tbs).
Between X-Com 2, Deus Ex MK, and Prey, I'm leaning in Prey's direction.