Galaga for Atari 7800
Top-down "almost scrolling" shooter, created in 1981. The ideas may have begun with Galaxian, but the more refined and polished Galaga was everything it wanted to be. More than just a Space Invaders clone, Galaga
was an instant arcade classic. With its oft-copied insect attackers and
clever craft abduction feature (shoot down the thieving alien to get
yourself a double cannon), it is still one of the most playable and
instantly addictive games ever made. Any self-respecting arcade still
standing is not complete without this timeless accomplishment.