For me it was Elton John and the Stones. I still think Goats Head Soup was one of the more underrated albums of the 70's.
But why the longevity for most 70's music? Rock N Roll started in the 50's so the music and lyrics were still very basic. In the 60's they progressed and some bands really experimented with different sounds and styles. By the time the 70's got here, artists and bands had perfected the simplicity of the 50's and the experimentation of the 60's to get a more refined, polished and professional sound. The lyrics too had been more polished into a more personal experience for the listener.
I am biased though, because 70's music is what I started on.
Biased or not, I think that's the best explanation I've ever heard. I now feel like I totally understand why '70s music is glorified in comparison to other decades (especially the '50s and '60s). I don't know if I fully understand your point about the lyrics though. What do you think makes the lyrics from the '70s any more polished or personal than those in songs from the '60s?