My earliest would probably be Space Invaders on the Atari 400.

But I also did a lot of PC gaming around that time - Alley Cat, Paratrooper, Prince of Persia, Dangerous Dave, GORILLA.BAS, NIBBLES.BAS - these were some of the earliest DOS games I played and still remember them fondly.

When we got a NES later on, spent a lot of time on Duck Hunt. And Super Mario of course, but don’t think I ever managed to get past level 3. Still had fun though.