Must have classic recordings

Classical is very difficult to find any sort of comprehensive listing of great recordings. All the 'little' lists just offer little dribbles of info. The best source is a magazine called "American Record Guide". They have an overview of some particular type or group. IE Beethoven Symphonies.
Worth going to a big city library that has all of them in reference. Ditto for music reviews in Stereophile and Absolute Sound back issues.
Also "Fanfare" magazine, another classical review guide. They only review stuff sent to them, so no major record labels, all the small labels though.
Then the Peguin Guide book, however, just like Grammaphone, very biased toward preferring British recordings.
NPR has a book, but it is very limited, best used to check out who did what worth listening to, rather than particular recordings of each composer.

Liz, you got game, girl!! Posting before church, no less! Much appreciated info there. Due time for me to organize all those classical platters!! Thanks

Furtwangler's 1942 Beethoven 9th, Berlin - the Hitler's birthday bash. Not because it's a great recording - far from it, it's pretty bad. It is, however, like being in the path of an oncoming runaway train and you are staring at it hurtling towards you and rooted to the spot, unable to move. Yes, you asked for good recordings but the title was "must have" :)

I don't know that you will get a lot out of a few "great recordings." Most people who are into classical music, myself included, find the genre to lend itself to a comparison of performances. For example, a great recording of Beethoven's 9th is one thing but the real enjoyment tends to come more from hearing the differences between performances by say Karajan in 62 vs Karajan in the late 70's vs. Furtwangler in the 40's or early 50's vs Vanska or Herrwegghe or Jarvi. Changes in tempo, how one conductor interprets the piece, the difference between the Berlin Phiharmonic as opposed to the Vienna, or how one conductor interacted with a given orchestra as opposed to another, and so on and so forth - virtually endless. To get much of anything out of classical music takes a good deal of time investment, but the rewards are remarkable. Of course, one can certainly find a well recorded version of any piece so as to say to company "listen to how great classical sounds on my system." For that, almost any studio recording in the last 10 years should suffice.