I've enjoyed watching for some time now, but lately i've become overcome with feelings of resentment and hostility. Allow me to explain.
What they are doing is not exactly comedy writing. Oh sure, they can write some sort of plot to keep the characters busy, and maybe they can catch some laughs with either Peter's funny laugh or the baby threatening to kill his mother. But the majority of their "comedy" comes from parody. This includes celebrities, 80's sitcoms and commercials, movies, etc...
None of it is actually original stuff. On several instances, they just put one of the characters in some famed situation from American pop culture (One example that comes to mind is when Stewie is rolling around a pinball machine like in that old kids thing with the song 1-2-3-4-5 6-7-8-9-10 .....11-12. I think it might have been a school house rock thing or something, sorry I can't be anymore specific than that). There was nothing original about it though and just the fact that the character was rolling around was supposed to make it funny all of a sudden?
Now sure, parody comedy is around and pretty funny once and a while (the first Scary Movie was pretty good). And I know there's nothing wrong with parody....but I'd venture out to say that this kind of comedy isn't exactly respected among most comedy experts (if there are such people).
Family Guy does have its moments though (characterizing Jesus as a regular white trash American always puts a smile on my face), and I probably won't completely stop watching it, but I certainly enjoy it less and less.