I’ve just skimmed the thread, so I’m responding directly to the OP, and my apologies if I’m repeating what’s already been said.
I think a lot of popular music is crap because it’s marketed to a mass audience, like a lot of popular movies, books, TV, etc. are crap because they cater to the lowest common denominator. Now, that’s not to say that you won’t get the odd Beatles thrown in there, but a lot of it’s going to suck.
So I think it’s hard to say that today’s music is crap if you’re comparing Britney Spears to Johnny Cash, but that’s because you’re forgetting Donnie and Marie (sorry, I’m having a hard time coming up with good, well bad, examples, I’m a youngin’).
I’m young and I’d say 90% of what I listen to was recorded before 1995, and probably half of that before I was 10. Not that there’s not a lot of good bands and singers out now, it’s just that the good ones from back in the day that have stood the test of time are better known than the new ones I have to stumble across on youtube or myspace (both great music resources, I have to admit). And shameless plug for my favorite band of the moment- Gogol Bordello. I posted a thread on them recently- if you think all modern music is the same boring crap that you hear on the radio, these guys will blow you away. Think gypsies on speed. Or acid.