If we go back historically, we find that only the most popular and/or best music stands the test of time. All the people that claim the 60s were the golden age of music because jazz, rock, folk, R&B, etc were releasing definitive masterpieces neglect the fact that there was also a ton of shit clogging up the charts and shops that we've subsequently forgotten about.
It's the same as it is today.
In this DVD that Thrill Jockey records put out awhile back, they go around to a ton of artists and ask them to talk about the album/concert/band/life moment that inspired them to be creative, or keeps them inspired, or re-inspired them. One guy, who's name I don't remember, says that all the albums he owns don't inspire him so much as intimidate him. He made the analogy that when Chicago burned down, all the great architects could start from scratch because there was nothing there to build off of or be too intimidated to change or try to top. I think there may be some truth to this, because from time to time I myself read things others have written and throw up my hands in despair because it's so perfect to me I almost want to quit writing entirely because I think I can never match it.
But the point that is missed is that, the more music we have, the more influences and the more things we have to build off of. Yes, some bands are derivative of older music, but I think today's music is just as fresh and interesting as the 60s best. Judging by how often I listen to different albums, I don't tend to favor any single decade or period from the last 40 years or so of music. I'm not saying that I think the Wolf Parade album is better than or will be as lasting/as important as something like Blonde on Blonde or Bitches Brew, but I listen to it as often if not more often than those albums. So today's music isn't better or worse than music from the past, it's just a different beast with different influences, different things to say, and different experiences to climb inside.