Good point. There is SO much good music from the past that you could spend several lifetimes exploring it all. The bulk of my CD purchases lately has been classical music off the Naxos label. The works of Bach, Beethoven, Handel, Mozart, etc., are stunning to listen to, even today. Very little "filler" on those works and they didn't need MTV to promote them. 400 years from now, we'll still be listening to Bach. Will people be listening to Britney Spears 400 years from now? You've got to be kidding. Ten years from now, most people won't know who she is just like most people today have no clue who New Kids On The Block were or Milli Vanilli. Pop music has become so disposable and forgettable that it's not worth the effort to keep up with it anymore. I have CDs I bought just a few years ago that are unlistenable. As a result, I am going to be much more discriminating about what to add to my collection.
If classical isn't your cup of tea, there are some great blues and jazz records available from the earlier part of this past century (1920-1960) that are just outstanding. Even the country music from those days was consistently good. They don't make country music like Hank Williams anymore!
Reminds me of one particularly funny Futurama gag. Frey was sitting in his room, depressed, listening to 20th century rap "music". Leela walked in and told him he shouldn't spend all his time "sitting around listening to classical music".