With out question, mine is The Simpsons. I'm a huge fan of satire and this show has that in spades. And who can deny the huge impact this show has had on pop culture not to mention it's constant references to the aforementioned. Half the fun of The Simpsons is figuring out what they're refering to.
Seinfeld is a close second.

BTW, anyone seen Titus? That show is a laff riot!