Some interesting thoughts simao. I just have to comment on one of them, however. While your high school seniors rarely listen to or aren't even aware of, for instance, The Band, that in no way proves they won't still be listened to in fifty years. Of course, I would say that, ay regulars ;-) ?! The Basement Tapes are considered The Rosetta Stone for the hippest of young bands and singer/songwriters today (hence the success of The New Basement Tapes album and movie), and those first two Band albums are a master's class in Rock 'n' Roll musicianship. Everything a musician needs to know in order to play the best Rock 'n' Roll is contained on those two albums. A bold claim, perhaps!
The same can be said for Kind of Blue by Miles Davis. An absolute landmark album that is unknown by most current music consumers, but it shall endure as a deep well for emerging Jazz artists. My nominees were made from the perspective of a musician, and though I myself don't care for him, Jimi Hendrix continues to be a hugely listened to (by young musicians) artist, as he will, I predict, continue to be. Maybe not by high school students, but, more importantly, by musicians. It is musicians who keep the music alive, not consumers. Lucinda Williams is a current artist keeping her music of choice alive, reimagining and interpreting her blues and folk influences.