I dunno,something on the ZX Spectrum. One of the few games I can remember the name of that I played was Starquake.
The original Legend of Zelda. Even though it was on a special edition Gamecube disc, I still count it.
Oldest games within my line of sight are duck hunt and Jet Set Willy. Both 1984. I thought my games collection more varied *Goes to buy older games*
Sadly, I've never gotten any of the Spectrum Emulators I've tried to work with any game I give it so I guess the oldest game I've ever played is Super Mario Bros. for the NES but that was on the Wii Virtual Console. The oldest game I've ever played on it's intended console was Super Mario Bros. 2 for the SNES which was released 1988. At least, I think so, anyway. There might have been a Game and Watch somewhere but I can't for the life of me remember which one it was...
Guess Space Invaders wouldn't count, as it came out in the 70s. I guess... NES Baseball? :/ One of the launch titles for that system.
either Donkey Kong or Galaga (both from 1981). I never really liked the original DK (could never get past the first level), but Galaga is and will probably always be one of my all time favorite games. Whenever I come across a Galaga machine at any arcade, restaurant, or amusement park, I just have to play it.