I've watched John Mcallister's internet streams twice for his world record breaking scores -- Joust and Asteroids. Believe me, they're real.
Once you've completely figure out a game, patterns to use or tricks to maximize your score, it turns more into a question of endurance than skill. Anyone can learn how to play a game and train your muscles to react quickly enough, but the real question is, can you play that game for 50+ hours straight to achieve a world record. Would you want to?
I surely don't have the mental capacity to stay awake for that long. I get loopy by the 30th hour.
