I'm not a big fan of the Simpsons, but they did have their moments,
such as the april fools episode some odd number of years ago:
The one where Bart puts the Duff beer in the paint shaker for hours and then sets up Homer to open it, as Homer goes to open the beer, Bart jumps out to say "Aprils Fools!!!" but mid sentence the beer blows up and there is a huge mushroom cloud like a nuclear expolsion.
I still think that is one of the best Simpsons moments ever.
But I haven't seen every episode and I'm not really trying to... while I find the Simpsons entertaining I don't particularly find it funny (some times its hilarious, most times its not, its almost always entertaining)
Family guy on the other hand is very unpredictable with the comments, flashbacks, and situations. Not to mention that they do some of the most stupid things that its just undeniably funny.
Arrested Development is probably the most unique show on Fox, from the narration ---> to the family relations, this show is funny in a different way than most other comedies I've ever seen.
Some people just don't get it but I just don't know how to explain it.