Family Guy. Oddly enough, I used to hate Family Guy even more than I currently hate The Simpsons. I thought it was the most retarded, stupidest show ever, and I thought anyone who watched it and thought it was funny were equally retarded and stupid, or simply following a trend. Like many things that are extremely popular in mainstream society, like Myspace for instance, I despised it and thought it was exceedingly overrated, and wished it would be canceled. The mere thought of it disgusted me.
But my best friend, Chris, eventually forced me to watch it one day with him. At first I was completely adverse to the idea, and glared at the television for the first three episodes, refusing to laugh at the lame jokes and witty comments the characters made. Then I saw the episode with the Kool-Aid man. Everyone said, "Oh no!" over and over again, and then the Kool-Aid man burst in like, "Oh YEAAAAAAH!!!"
I laughed. Hard. And from then on, I loved Family Guy. xD
Family Guy got old on me really fast after it came back. The original three seasons were FANTASTIC, and the first season after it came back was pretty good. After that though, the really funny stuff was few and far between for me. It seems to me that they are relying to heavily on drawing things out ridiculously long to get laughs.
The Simpsons took roughly nine seasons before it started to lose steam.