All of them are good.
My favorite episode of Family Guy is when Peter won't take off his red pajamas and goes around shocking everyone.
My favorite episode of Futurama is the very first one because Bendy tells Fry to bite my shiny metal @ss.
My favorite episode of American Dad is when he puts his family in the chambers to make them think they are on vacation.
Sorry they all make me laugh to hard to pick.
Family guy is a little bit better though because there are always really entertaining jokes in between the main plot so your never bored and always laughing.