Family Guy is great. I like it, I laugh, but... South Park is of better quality.
Family Guy makes me laugh, and has it's own little charm, but South Park is brilliant in my opinion. Not everyone can stomach the "jokes", but when you actually sit down, watch the show, and "think" about what the writers are saying (yeah, I know, thinking while watching a TV show? Hahahah, how funny) it actually makes some sense and is pretty well-written and coherent.
Family Guy kind of has a quick-laugh quality while South Park aims for something higher. Futurama is somewhere in the middle and is fun, easier to watch with the folks, and pretty damn cool. Thus Futurama owns all.