Keeping in mind that these are "important" games, not necessarily the most popular or my personal favorites:
1) Pac Man : First example I can think of of a MAJOR commercial, merchandising, and cultural phenomenon.
2) Super Mario Bros. (NES) : Redefined the role of the console game into something more than a quick 30 second jaunt. Redefined platformer genre.
3) Dragon's Lair : Revolutionary use of new technology for the purposes of gaming.
4) Doom : An early example of outrage caused by video game violence, and would set the stage for violent 3-D shooters after that.
5) E.T. (Atari 2600): Showed that a commercial tie-in doesn’t always guarantee success. Notorious for it’s complete and total failure.
6) Pong : Just for historical purposes, really.
7) Final Fantasy 7 : Redefined the RPG on the console forever.
8) Zork : Example of early RPG and immersive game play. Set the stage for story-driven gameplay.
9) Myst : First example of near photo realistic graphics in a game. Set the stage for all game graphics after that.
10) Tetris: Pioneer of puzzle/block games. However, also a good example of a game being released WITH a console that was arguably one of the best titles for it.
