I feel like an old fart saying this, even at 29, but I think of what's popular now, and whether when the artists are 90 years old, if they'll still be saying they are truly proud of all the work they did. Rhythm or not, not many songs have become "epic" with lyrics like such that are popular today.
Hard question to answer. Musically, from the last 50 years or so, Hendrix certainly. Hopefully some bands that have changed what music is: Husker Du, Hum, Frank Black, Geradine Fibbers, etc. There's a very real chance acts like Public Enemy and Ice-T will be, because of the social commentary. I don't think anyone listened/listens to folk music for the "music" part. You can just never tell. Many of the revered classical composers were actually ignored during their lives. Not all, obviously, but far more than you would expect. Everyone will say the Beatles or Elvis or something like that, and while they will most likely be remembered, I guarantee you some mostly unknown band that less than 10000 people even knows exist today will be touted more than the Beatles 500 years from now. That's just how it goes. The last couple of decades have changed music forever though. Before the mid-to-late-80s all forms of media that music was recorded upon degraded. Everything would eventually be lost, just as it had always been. CDs, however, can last for 100s of years, and digital files can be transferred literally forever. mp3s will honestly change the future history of music more than anything ever except for maybe the phonograph.
I think that I've answered my own question lately: Whilst not "epic" in terms of orchestration, I can bet that some current Christmas music will be played in a century or two. I'm listening to the local Christmas station, and stuff from Cyndi Lauper and 98 Degrees are right in there with Bing Crosby like nothing's wrong. This year, I think, Norah Jones joined the crowd. They seem to just add in more when artists make them. Not all will survive, but I bet a few will continue.
Ween - Hey there Fancy Pants
That song WILL be taught in college classes in future generations.
