i'd like to disagree, joeamis.
getting a high score at a hard game such as donkey kong is based on repetition. many of those classic arcade games had limited ai. because of that, memorizing a simple pattern was often enough to get though an entire game with a high score. (pac-man comes to mind.) thus, it becomes an exercise in remembering what to do and when, instead of reacting to the game.
also, i hear that the guy who beat smb3 in 11 minutes cheated. he used an emulator to slow down the game, and he would save repeatedly and load the game if he messed up. then he went back an edited the video.
i actually noticed what i thought to be a glitch in the video in one of the tank levels (i can't remember which one) where it looked like mario got hit by a cannon ball, then magically warped above it and jumped on it. i passed it off as being a problem with the direct feed. looks like it might have been a case of creative editing.