I consider myself as big a KJ fan as anyone. I've got many of his recordings and all of his dvd releases of the Japan concerts, which most were recorded from the mid to late 80's. His trio work is the best place to begin I would think because it's timeless stuff that sounds like his current recordings.
Anything with Keith Jarrett Trio will be a winner. Blue note did a 6 disc recording from a live NYC appearance. His best album, imho, although not found on vinyl would be: live at the deerhead inn, recorded near his hometown in PA
Keith has been recording/touring with Gary Peacock and Jack DeJohnette for decades now. Probably the longest running jazz piano trio ever. He did a stint with bassist Charlie Haden yes, but that was decades ago.
Checkout the LaScala disc, which is a live performance of an Italian concert. Over the Rainbow is the real gem there...it's one of those performances one can listen to over and again, for KJ's harmonic approach to the tune stretches this well known standard to never before heard levels of the tune by anyone, and his delicate touch on the tune makes it a must have. I spent an entire year absorbing a note for note piano transcription of the tune at the piano, so perhaps that gives you some idea of the tunes merit.
Personally, I almost prefer viewing his live trio performances on dvd, to listening to him on audio. There are 7-8 of them available, which can be located as best buys on the bay. Someone else may chime in regarding his classical recordings, but anything you find in a used record store of his KJ Trio stuff will likely be a gem. Standard I and Standards II are both excellent recordings. Most of the KJ Trio recordings of the past 2 decades all have excellent jazz standard interpretations. Keith is a master of reworking jazz standards. Check his version of God Bless The Child on Standards I...he rewrites the tune rhythmically and embellishes it to a degree that only KJ can do. Most of his KJ Trio is can't miss stuff, so that's as good a place to begin as any. Enjoy!