Used to love South Park, went through a phase of watching The Simpsons, never really got into Futurama but LOVE Family Guy. Me and my fiancée watch it the Friday following its new US airing with dinner. Never fails to make us laugh.
I think the humour appeals to a wider audience than Family Guy, American Dad, etc...
Its just none stop funny stuff, with a nice warm funny message at the end, I never really understand Family Guy, its random stuff thrown together by manatees...