I don't think so. The Simpsons remain fantastic, no matter what happens, although I'd honestly have to admit, the newer seasons are kind of cliché. They usually contain old jokes from the previous seasons, the base, that is.

As that is, South Park's humor actually doesn't even come in comparison with the Simpsons, in my personal opinion. Family Guy on the other hand does, it frequently contains fresh and new animated scenes, and amazingly enough, it never gets old, imo.