M*A*S*H is probably my number 1. A show that can make you crack up and cry in 22 minutes.
Seinfeld is absolutely brilliant, but it's not my favorite. Best ever, yeah, maybe, but it's hard to put it at the top of the list when none of them are likeable. Which I know is the point, but...
Do the Simpsons and South Park count?
the best one I have seen in recent years is Parks and Rec.