Rolf - get that from the 3rd Kraftwerk record, Ralf und Florian? Just kidding, that's obscure even for me.
Yeah, things are a lot harder to sustain then to get going. You lose a lot of enthusiasm (or youth) and you use up your best ideas up front, so the further you go, the more you have to reach - hence Fonzi jumping the shark in a leather coat.
But I'm with your brother, if by offensive he means (as most do) sexual, semi-sexual and body fluid humor. If vomit, poop, pee, pus are funny, then Family Guy is direct from the gods. It's going to be hard for anyone to ever get much grosser than Brian doing a rim job on Stewie after Stewie pooped himself. That's pretty gross.
South Park goes after a lot more stuff than cheep sexual references (and hey, gigidy, gigidy nothing wrong with cheep sexual references) political, social and cultural stuff, and they really go after the cult of celebrity in a big way too. (And more power to them for that too.) But South Park offends people in a non-sexual, non-gross way, and face it, half the people in this nation are too frickin stupid to get half the real jokes on South Park anyway. But Family Guy, they once put a reference to a Cleveland Steamer into a bit about Louis and Meg being street walking prostitutes as Peter fantasies about picking them up. That pretty far out there too.
she was accepted by Quagmire
What's that saying, that Quagmire thought he might get lucky with her. Like he is all that picky? Hell, the crack of dawn is not safe around him. He's like John Fitzgerald Kennedy for crying out loud.