The Simpsons gets old after a while. South Park does too, but it's pretty funny most of the time. I would say the Family Guy is the only one that is unpredictable so I think that it is the funniest.
Two to be canceled? Dang, I love Family Guy and South Park. As long as one of them had a great end to it and the other kept going I wouldn't mind which.
The Simpsons
American dad, the only show completely run by Seth. i love it
South park wins on my side.
I think the Simpsons' best episodes are better than Family Guy's best, but Family Guy is more consistent. Like the Haircut Brothers.
Don't much like South Park though
I think the Simpsons' is a comedy about classic humor.
Family Guy is a comedy about stupid stuff that's humorous.
Based on my age, I'd go with Family Guy because the jokes are more modern.