a consequence of Sturgeons Law combined with the passage of time: As new material is released, the vast majority will be of mediocre or worse quality, but over time, a powerful selection pressure causes all but the best 10% (or even best 1%) and worst 10% be rapidly forgotten, leaving an increasingly inaccurate impression of the overall quality of the genre over time.

Yes. This is why nobody remembers how popular Grand Funk Railroad was. They fell into the middle of the bell curve, that nobody remembers. The top 10% of the early 70's would be things like Zeppelin, Sabbath, and the Stones. The bottom 10% would be the "mellow gold" and "easy 70's" type of music that you see being sold in compilations advertised on VH1. The kind of music that people remember mostly because it was so horrible. The rest of it, is simply forgotten.

Ironically, I don't think this applies to television as much as it does to music and movies. I am 100% sure that TV now, in 2007, is better than it was in when I was a teenager.

The golden age of network TV is now. I don't watch many shows, because most shows still suck, but the few I do watch are the best shows evar.