I think you are looking for titles a little off the beaten path so my nomination is for Col. Bruce Hampton and the Aquarium Rescue Unit - self titled live album. These guys are sort of a cross between the Allman Brothers and Frank Zappa and the album is one of the best live recordings in my collection. The musicianship on this album is stunning.
What is the VERY BEST CD album you've ever heard?
Just like with records, I came across releases on CD that were never popular, but bring lots of interesting music and so I started collecting CDs that do have collectible value for the reason of a great and rare music presented.
So far album "Sauce Hollandaise" by Ashra is on my #1 desirable list
"Best Band You've Never Heard In Your Life" by Frank Zappa is my 2nd best CD I've ever heard.