I also grew up loving the Simpsons, and still love the idea of it being on tv, but as everyone knows the quality has dropped off a cliff in the past 15 or so years. I really don't pay attention to any of the new episodes. But the old episodes are still treasures.
I came in to post the Simpsons, and see that you beat me to it. It's actually been about 20 years since it
started declining, but it was 15 years ago that the low quality of the new episodes caused me to stop watching the show. I don't know what it is, but it seems like every comedy show that runs long enough devolves into random events plots with lazy jokes, almost as if the writing staff forgot the basics of comedy.
I still love the early seasons of Simpsons, but the fact that the show has been junk for the majority of its run now makes me embarrassed to admit to liking it. Comedies have a bad habit of greatly outstaying their welcome, which makes it all the more significant that Jerry Seinfeld chose to pull the plug himself when he was offered a tenth season for his show.