South Park has evolved to be more about the town than about the four main characters like it was before. Simpsons has Springfield and Family Guy has Quahog but it seems that the nature of those shows can't seamlessly incorporate the town into the plot on a episode by episode basis like South Park can. I think that's because South Park formats each show like a thriller movie and they use parody movies or other pop culture phenomena as a template in each of their episodes and this allows them to make the plot around the town as opposed to the characters.