Chess. Face to face with a real human probably is the best game to play to keep the mind working well.
When I was a kid, my grades would go way up in those periods where my father would play a few games of chess with me during the week. Decades later, after he came down with Alzheimer’s he seemed to do much better overall, when we started playing chess again, although it was sometimes difficult to get him to keep his mind on the game.
I have an old friend who is president of Mensa for a fairly large area. He loves chess. He has tried to get me to take the Mensa test but I just don’t care anything about it.
I will say that when we were both young I scored about the same thing he did on achievement tests in school and we both scored in the top percentile.
Anyway I have tried him in chess a few times and he absolutely kills me without really trying. On the other hand, I can beat him in checkers.