South Park must lose here. Married With Children has a much, MUCH bigger cult following and is a much more entertaining show than South Park. I'm still bitter that Seinfeld lost to fucking South Park, but Married With Children is a much better show and no one should dispute that.
How exactly is Married with Children the better show? Both shows are well known for their boundary pushing, vulgar material. I've yet to see anyone even try to refute my comment that MWC is nothing but live action version of a raunchy animated comedy.
Married with Children is your archetype, basic comedy that follows the same pattern set up by Shakespeare centuries before. Character starts out in a neutral position, character suddenly finds himself in better position only to lose everything halfway through the episode having found himself in a worse position, by the end of the episode the plot works itself out and the character ends up back in a neutral postilion.
If this was half a decade ago, I would have voted for MWC because South Park was little more than toilet humor with little character development (like Aqua teen hunger force, or Family Guy.) I believe the turning point for South Park's evolution was the episode Trapped in the Closet, in which they made fun of Scientology in ways that the religion had not been made fun of before. After that episode was banned, you can see the transition of South Park from raunchy toilet humor, to clever spoofs on current events in society.
While these spoofs are sometimes ridiculous in their portrayal, the messages the episodes send really aren't that far from reality. I've already given Internet episode as an example, others include the euthanasia episode with Kenny, the plight of the broken beaver dam with Eric and Stan, and the new episode Whale ****es, which has a deeper message of the American economy and the wastefulness of our resources. These are just a few of these types of episodes of South Park that satire current events but deliver a truthful message behind them.
South Park is much more than just a raunchy comedy, it caters to the social norm while delivering a message that anyone in their audience can understand and appreciate. Married with Children is a comedy that followed the same consistent pattern with little evolution in their product at all.