One of my favourites I'm currently going through and watching from S1E1 right until the latest episode, currently 10, almost 11 seasons in and I do think the first 4 or 5 seasons were better, and the feature-length episodes do get a bit tedious, but overall I just think is comedy gold. It's not a classic comedy, it's more ridiculous, childish things that make this show funny - the low maturity level of Peter, the cutaways, the ongoing jokes with the chicken and THAT song.
I watch an episode every day with my dinner, often two a day in fact. Whilst some episodes often pass me by without making me laugh and are forgettable, 9 times out of 10 there's a few moments in every Family Guy episode that make me crack up!
Not one to watch with the family, but certainly one I'd recommend.