I'm nominating some that were extremely popular and/or brought something new.
Gauntlet (four players could play as long as they could afford.)
Ms. Pac Man (the premise of Pac Man with several mazes and without the screen 255 glitch)
Donkey Kong (brought us "Mario" but also just extremely popular.
Star Wars (but only the machine with the cockpit)
Galaga (Fairly basic premise, but still popular today.)
Double Dragon (first two-person, fighting game that I remember)
Out Run (or Pole Position, for a driving game)
Dragon's Lair (laser disc, plus hand drawn animation art--on the downside, the first $0.50 game I remember)
Frogger (best soundtrack of early arcade games)
Golden Tee (I actually never played it, but popular)
NBA Jam (I didn't play this much either, but another popular sports arcade game)
Centipede (gave us the trackball and was the first game designed to appeal to women)
Super Off Road (race two of your friends around dirt tracks with jumps!)
Track & Field (one of my favorite games. I think drummers had the advantage when you had to alternately hit the two buttons to build up speed.)
Mine are mostly from the early days of arcade games because that was when I was in the arcades. I left off some of the originators because I wasn't sure they would have a chance at "best." They'd probably go farther in a "most significant" tournament.
