Battleship is the best game I know of to introduce basic coordinate geometry. And it’s a lot of fun. If for some reason you’ve never played it: Each of two players places ships in a “sea” of labeled rows and columns. Then players take turns guessing where the other player’s ships are. Players are required to say whether a guess is a “hit” or a “miss” and whether a “hit” results in a sunk ship.
There’s some strategy involved; you have to be careful not to inadvertently let slip a detail that could help your opponent. (My five-year-old is terrible at this.)
And of course the game can be good for learning sportsmanship. A significant amount of luck is involved, so hopefully kids learn to be gracious if their opponent gets lucky and wins.
My five-year-old is not quite ready to play on his own, but he enjoys playing teams with an adult.
Of course you can pick it up through Amazon (paid link) if you don’t have an old set laying around.