A game I'll still play in 20 years?
I know this is a cliche answer but even at 73 I can picture myself playing some flavor of D&D.
I haven't played D&D in a few years and I've turned down invitations to play in the future. It's not my preferred game. But there's something about sitting around a table rolling up a thief or a magic-user that seems evergreen.
Nor do I think I'll have any problem finding pick up games of #callofCthulhu or #DeltaGreen online somewhere.