Married With Children. I still watch it every time it's on television.
I think the reason these shows beat out the likes of The Sopranos, Seinfeld, The Wire, etc. is because people watched them at an impressionable age, so it's pretty hard to go against them. I for one, grew up watching Married With Children, In Living Color, and The Simpsons - I watched them religiously. It's probably the same for a lot of us. They're great shows regardless.