I don't mind Family Guy (American Dad and the Cleavland Show are absolute garbage), but the McFarlane shows all share one giant flaw. The writers have no idea how to write a story. They can get the concepts down, they have conflict (point A), and a resolution (point B), but they don't know how to get there. All those absolutely random moments that feature very obscure references are story progression for these shows, and while some if it is funny, it's just not good writing.
It's the big problem with the Simpsons these days too. While they used to be masterful storytellers in their heyday, nowadays they've evolved the show into a more big picture scenario, and there's a huge disconnect between their main focus for the story and the events that surround them to get them there.
That's why shows like Old Simpsons and Futurama, and yeah, King of the Hill, will ALWAYS be heads and tails above Seth McFarlane projects and the like