Yes, I've tried to figure out just what it is that I don't care for about The Simpsons, and I can't quite put my finger on it. The writing is excellent (I've seen enough of it to know that), and I'm with you on the artwork, Roger - when it first hit the screens I hated the simplicity of it all, but now I'm happy to acknowledge the brilliance of that, especially when they include 'real' people.
I know it sounds petty, but I think it's the voices. Cartoon voices annoy me (I'm sorry if that's voicist). One of things I think I enjoy most about the best of the CGI animated films from the likes of Pixar is that they (mostly) use 'real' voices, often very well known ones at that, and not some actor with his testicles in a vice to dub the small characters, or another with his larynx expanded by a 6" grommet to voice the villain.
My logic falls down however when I think back to my childhood, and the great voices of Donald Duck, Tigger, Tweetie Pie et al. They just wouldn't be the same without the voices, and I loved watching those any chance I could get. Perhaps I burnt myself out back then?
D'oh!