"The Contest" is one of the most recognizable episodes of television and really set the pace for what a sitcom is supposed to be. One story, one idea driving all the characters toward a common goal, with some funny detours along the way.
The episode is legendary because of its execution, how they could have such a raunchy topic without even mentioning it by name.
This is one of the reasons Kramer became an icon, for distinguishing characteristics and behavior like this and why he is one of television's greatest personalities.
You would be hard-pressed to find a more meaningful episode of television for a series than this.