It seems to me that Seth MacFarlane has run out of gas with Family Guy. For quite some time I have had the feeling that it's lost the punch that made it famous. MacFarlane himself admitted in It's a trap, the third part of the Family Guy Star Wars Special, that he didn't want to make it, but was "forced" with both money, and the permission by Fox to make his own movie if he made it. It was not even written by him. Greedy basta...
Since the decline of the quality of the stories it seems they want to attract the viewer with little more than eye-candy, such as increased use of CGI instead of old fashion drawings - which are also done with the aid of computers, but in all cartoons (The Simpsons, South Park etc.).
Even shows of the "Road to...", which are usually praised by the fans are in my opinion of lower quality now. Like Road to the North Pole from December 2010. Even though, according to the Wikipdedia article, it received positive reviews, the previous "Road to..." shows were better.
For more than a year now I've preferred American Dad! over Family Guy. It's like somebody other than Seth MacFarlane has full control over it. It's fresh, funny, and has punch just as the older seasons of Family Guy have.
Maybe Seth MacFarlane needs a third cancelation of Family Guy to wake up. Or perhaps he should just leave the show and hand it over to others. Then he can do his singing and other things no one really wants to see. If so, he could soon be forgotten.
While Fox is on canceling - the shouldn't forget to cancel The Cleveland Show. In my opinion it's just boring. Even more lame than Family Guy. I would guess that the only reason it has any positive ratings is that it serves as a bridge in the slot between American Dad! and Family Guy.