I don't think it's a case of nostalgia, and I think it's terribly ignorant of you to say so without actually sitting down and listening to an album or something. I hardly listen to any Led Zeppelin, but from what I've heard they have some seriosuly great songs, a lot of variety between heavy and soft stuff, etc. Obviously music has progressed a lot in 30 years, but when we listen to music from the past, hopefully we can remember how influencial and powerful it was for so many people.