Well unfortunately that's what happens when a series is run into the ground. A long running show is good only if the quality remains. But I don't squarely blame Simpsons, as much as I love the show that I think "outclassed" Simpsons, I do think Family guy helped.
Family Guy introduced a new kind of humor that I don't think everyone was ready for when it first came on: random crap. Robot Chicken, Harvey Birdman, and Perfect Hair Forever are signs of what kind of humor people really seem to like these days.
Family guy literally pulls anything and everything out of their ass. They parody stuff from everything: The Bewitched movie, GI Joe, Transformers, Superman, Bed Bath and Beyond, Spider man "Everyone gets one.....ONE".
I loved that one.
I think Bloo has actually changed from nice guy prankster to pain in the ass actually. I still think Bloo is a good guy deep down but if you watch how he acted in season 1 and what he's become now, he's lost A LOT of his good side.
That is part of what makes him funny but he's probably the only character I have ever seen who has regressed rather then evolved. Which like I said, is still funny.