That's a really good point Mekalon. The lists I have found all have a slew of comments following them with suggestions for inclusion or replacement. Everyone is going to have their own opinions. Look at Lwaxana Troi, she has a whole storyline in TNG yet some folks hate her and the episodes she is in. Obviously her detractors would not say she is part of an essential experience while others would want her storyline included.
This is tough.