South Park > Futurama > King of the Hill > Family Guy originally > American Dad > Family Guy now
I'm not mentioning the Simpsons until I give the series a proper watch-through as an adult. I remember some great episodes from childhood, but it'll take more than that to find a personal place in this argument.
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http://img812.imageshack.us/img812/3492/eponaharr.jpg
Nominate SuperNiceDog's Guru-choice, then Epona.