1) Pong
2) Space Invaders - Rise of Arcades
3) ET - The point everyone credits as the turning point toward the market crash
4) Super Mario Bros - Best selling game ever(40 million copies), characters and formula still exist today, was a great game that people still love to play and much more
5) DooM II - Technological Achievements
6) Quake - See DooM but for 3D
7) Super Mario 64 - I view this as a precursor to many games. Grand Theft Auto III even. Mario 64 had open ended gameplay. You could just go into a world and do whatever. No real set path on how to beat the game. Many others tried to copy the success it had as well.
8) Metal Gear Solid - Redefined what a game can be with presentation, story, graphics and more. This was further realized by its sequel Metal Gear Solid 2. Some would argue FFVII and I think it nailed the presentation but not on the story aspect or the way the graphics were utilized to tell the story. Not to mention that Metal Gear had much better localization(Noles Pole anyone?).
9) Counter Strike - While not the first online multiplayer game, I think this is the one that brought online gaming out in a big way.
10) Reserved for when someone finally does something monumental with the Wii.