Old Games that are Still Alive and Kickin'?

Lord Grey asks: "Recently I was killing time while debugging a long-running program and decided to fire up a copy of Shanghai II -- a Mahjongg game for the Macintosh. I've had this game for years, faithfully moving it from computer to computer while keeping pace (more or less) with the newer hardware. I started wondering if there were other people out there that just hold on to those old games and, if so, just how old are they? It would be interesting to see what the oldest game that still runs on current hardware is (my Shanghai II dates from 1991). Or am I the only one that's clinging to the past?"