Futurama is just so much smarter in it's jokes, characters and story lines. Family Guy relies on slapstick humour and more flashbacks than I can count, overall it's just a dumbed-down version of The Simpsons and of much lower quality. Futurama has also never seen a drop in quality, it has been consistently hilarious throughout it's run but Family Guy on the other hand just gets worse every year until the only joke in the later episodes is the show itself.