Our family got an Atari some time in 1979, when I was 5 or 6 years old, and my first game was Air Sea Battle:
http://www.mobygames.com/game/atari-2600/air-sea-battle You had a gun/cannon at the bottom of the screen and aircraft were flying back and forth overhead (in straight lines, at constant speeds). You could “aim” your gun in one of three angles. And then you shot at the aircraft. It was basically a shooting gallery. There were some variations where you could change the types of aircraft, or could be a submarine shooting up at boats. Or you could play with two players simultaneously, with each person controlling their own gun and competing for the highest score. There was also a two player version where one person was a plane flying across the top and the other was a submarine floating across the bottom: you could speed up or slow down, but you were still confined to moving in a straight line across the screen, and you shot back and forth at each other. And that was it. It was fun for a while (more so if you were playing with a friend), but not something you’d get so engrossed with that you’d play for hours at a time.
Amazing to compare that to any modern game and see how far we've come in 35 years.