HI TO ALL... Made a change to isolating my speakers, so I'm pawing thru my CDs and listening for the changes/improvements - and I put in one of the all-time greats (IMHO), and I am still so disappointed in the quality of the recording:
BAT OUTTA HELL by Meatloaf (luv ELLEN FOLEY ON "... Dashboard Lights..."): UGH!

What are your personal disappointments?

Another for me: THE DANCE by Fleetwood Mac : OVERLY Bass heavy
My limited experience with Buffalo Springfield has me posting here. Their lps sounded awful until I heard the "What’s That Sound" box. What a transformation!
I recently listened for the first time to an OP of Bruce Springsteen "The Wild, The Innocent, and The E Street Shuffle". I really enjoyed it but found it to be a little on the bright side, certainly not reference quality.
@slaw, I was very familiar with the three Buffalo Springfield albums (my High School garage band included their "Mr. Soul", "Bluebird", and "Hot Dusty Roads" in our "repertoire") by the time my teen combo opened for The New Buffalo (BS drummer Dewey Martin and three hired sidemen, one of the Bobby's brother Randy Fuller) in '69. Dewey had sounded somewhat "weak" on their recordings (their "producers" were amateurs), but not so live! I got a valuable drumming lesson watching and listening to him play my Ludwig drumset in that Monte Vista High School gymnasium. Turned my notion of what good drumming is on it's head, in fact. Bye bye Rock band drummers, hello studio musicians!
Historically, most recorded music was only listened to on consoles and record players. 99 percent of consumers (including recording artists and engineers) never cared about "high fidelity". I've talked to dozens of musicians none of whom own decent playback equipment. Ironically, the one format released to cater to connoisseurs was prerecorded open reel tape which actually sounded worse!( I sent Mason Williams an open reel deck so he could listen to some of his own tapes. He was kind enough to send me copies). It's almost a fluke that many records sound as good as they do. 
Most Simon and Garfunkel records.
@ slaw 

shows how different sounding masterings can be of the same music. My UK version is actually little dark with beautiful vocals (lots of 3D). Reference to me because I can play it at any level without hearing fatigue. The same for a newly accuired vinyl of Lowell George Thank's, I'll eat it here. Superior to the cd transfer.