I skimmed through this thread, and I would like to make further comments.
First, some old shows really did suck. This time, I'm not talking about the racist ones. Here are some examples:
Cow & Chicken
Tiny Toon Adventures
Kablam, that's it.
It makes me look back and ask my self, "Why in the hell did I watch this crap?"
Of course, though, the new cartoons do indeed suck. The butt humor in My Gym Partner's a Monkey just competely grinds my gears. Other shows like Rocket Power really sucked with its annoying characters and lingo. Some others I don't watch, like Squirrel Boy, but I bet they are terrible.
The real treasures in cartoon history would be shows like Animaniacs. Heck, I even like the original Scooby Doo for its corniness, the way they use the same music and practically do the same things in every episode. Same thing with Doug, with its corniness that was actually funny. Rugrats was somewhat a gem as well, as that was probably the main cartoon I watched when I was little. New shows like Avatar are pretty good as well. And of course, there are some good animes that existed throughout time.
Edit: I'm sorry to those I offended that liked Tiny Toons Adventures. I just have an irrational hatred of that show, that's all.