This will sound cliched, but of about three-hundred jazz albums that I've heard, Kind of Blue is still the best. The mood and musicianship is astonishing. It's the kind of album that continues to reward me, even after dozens of listens.
As for jazz in general, I think that it functions best as mood music. I listen to it while I'm reading or studying, and I find that it helps me focus. Appreciating jazz, I think, is about stepping outside the conventional music listening experience. If one does not look at albums as coherent wholes, then jazz will be difficult to enjoy. Of course, that's not to render any judgment on anyone's tastes - rather just a general appraisal of how jazz works.