For me, the classics are culture. Not only have I watched stuff from 80s & 90s, but I loved some of the stuff from even farther back. The only few shows today I enjoy watching was Avatar: the Last Airbender (great story, great depth, good comedy), Krypto: the Super Dog (I just like dogs, and it reminds me of Road Rovers), the Land Before Time series (obviously), the Simpsons (a still-living classic), and American Dragon: Jake Long (it's funny, and I like dragons).
The main reasons I don't like the others is that it's not as intellectual in comedy, to me anyway. The characters are simply too crazy to me.