I think you're giving the show a bit too much credit, but then again it's all in the eye (and ear of the beholder). To me, it got dumber and more obvious over the last several years. A few months ago I caught some episode where Lisa became addicted to an iPod, only it was called the "Mapple myPod."
The show used to be really sharp and had this element where there were these subtle, smart jokes for some fans...and then the slapstick silliness for mouth breathers. But the show jumped the shark somewhere between going to NYC and Tokyo. Now it's this really obvious attempt to charm the hipsters who still watch it but it fails double time because the animation is so laborious that the current cultural jabs end up showing up way late to the party.
That comic episode with Alan Moore, dude? As a life long comic nerd, I should have been geeking out, but instead I cringed. It was obvious and sloppy pandering to the hardcore base and must have come off as complete, boring nonsense to non-fanboys.
Family Guy is what it is. It's raw, line blurring, blunt jokes and cultural shoutouts for the 25-35 crowd.
Neither holds a candle to South Park. Now that's a show that continues to get smarter and, somehow, funnier with each season.