I think my favorite is pre-90s Joni Mitchell. I also have been a reluctant fan of Tori Amos for years. In some of her less "pretty" wallflowery music you can tell she was enormously influenced by LZ and Plant.
I can't bring myself to choose between Celebration Day, SIBLY, Out on the Tiles, Tangerine or That's the Way. BYA Stomp, Friends and Immigrant could all be my faves as well depending on the day. The only one I think is not as good as the rest of the album is Hats Off, but I still love it and appreciate its contribution to the album. III is perfect, by far my fave.