Depends on if you qualify it by how often I play it. I mean, I just recently finished a beating every single scenario in the SNES Aerobiz and Aerobiz Supersonic. I'm not even sure what year those came out. On the PC, I've got Diablo (1996) and Protostar: War on the Frontier (1993) as well as Syndicate and SimCity 2000 (all 1993) installed, but haven't fired them up in a while, and if source ports count, I got DOOM (1993) and Duke Nukem 3D (1996). I have a Herzog Zwei (1989) rom for my Genesis emulator, but I haven't played in quite a while...
And that's as far back as I'm willing to go right now...
Ah, Herzog Zwei memories... I think I'll go fire it up RIGHT NOW...