Butters on South Park said it best:
"Simpson's did it."
They have been on for so long that it is assumed that they are the best, and for the most part they are. The first ten seasons were great. Then I think all those involved with the show checked out for a couple of years. Recently they have been on an upswing, but I don't think they'll be around for much longer.
I vote for The Simpsons.
