I'd say the current hierarchy is in general Futurama > American Dad > South Park > Family Guy > The Simpsons
I give Futurama the points for originality. American Dad is just a better version of Family Guy that isn't trying as hard. South Park is pretty good but imo the actual humor has gotten a bit predictable, but that may just be because I've watched so much of all of these shows. The Simpsons simply isn't any more, I hate to say it but I think their time has come to an end.

Hello Grandpa my old Friend... - YouTube