I debated whether I should post my answer, because mine was a LONG time ago. But encouraged by the posts about Super Mario Brothers I decided I would post. The last game I beat was Donkey Kong! And I beat it when it was a NEW game!
And then for many years I didn't play games. Now I play with my boys. Does reaching 1st on the leader board of io games count? If so, I could claim beating diep.io.