Mount Rushmore: Sitcoms

For the 4th installment of my periodic series in which I select who/what I think are the 4 ultimate in a given category, I'm focusing on sitcoms.  Because there are so many shows I feel are worthy of being up on this Mount Rushmore, it was hard as hell narrowing it down to just 4.  Please note that these aren't necessarily my favorite sitcoms.  However, when it comes to quality and influence, the