Not because it's the best album in the world (let alone the best show in the world) but because, arriving as it did in 1981 and being the daddy of all Cats recordings, this is the only version with a single shred of originality. Obvious perhaps, seeing as it came first, but it's actually quite unique.
This is why:
It's the only album with sufficiently powerful orchestrations - listen to the Overture or the Jellicle Ball to see what I mean. At the same time there is shade and subtlety not found on other recordings.
It's the only album to feature the original, full length versions of Bustopher Jones, Mungojerrie and Rumpleteazer, Old Deuteronomy, The Ballad of Billy McCaw and - most significantly - Memory, which was subsequently torn to bits for Broadway and other productions (sadly even London).
It's the only version to pull together such a mass of new and established talent - Bonnie Langford, Sarah Brightman, Jeff Shankley, Brian Blessed, Paul Nicholas, Wayne Sleep, Elaine Page.
Finally, it's the only version of the show which has an individual, un-sausage-moulded sound, be it orchestrations, musicianship, production, or vocal interpretations. Almost all other albums which followed are identical to each other, but this one stands out. The possible exception is the Broadway cast album, in which Betty Buckley tears Memory to shreds. Dreadful perhaps, but at least it's memorable!
Cats is supposed to be, and be about, magic, and this album has it.