Yeah, I think the "South Park" in the series is more or less based on Denver. Everytime they heard some weird story while growing up, like a cow being found with three heads or whatever it always happened in South Park, so they used that name for the fictional town.
There are loads of South Parks around the world. There's one near Reigate in Surrey.
I think there's one near Banbury.
There is a South Park in Colorado near where they grew up though, which they said in an interview they took the name from.
I can't stand it either: the characters are annoying, the writiing is shocking and I just generally don't find it funny.
And those voices! ARGHHHHHHHHHHHHHHHHHHHHHH!
Still love it!
I don't watch it avidly, but enjoy it when it's on.