I find many of the posts in this thread completely mystifying. My collection is not as big as that of some, no doubt, but it does extend to over 2000 classical music CDs. A lot of it is opera, but a lot of it isn't. It ranges from early music, like, say, Masses by Leonin and Perotin, to the present day, with CDs of music by John Adams and James MacMillan. Chamber music and instrumental music is probably under represented, though lately I find myself enjoying more of it. I confess I still find much of the music of Berg, Schoenberg and Webern and their followers pretty impenetrable, so not much by any of them. I do have Karajan's set of orchestral music by the big three, but, though I enjoy some of the earlier works (Schoenberg's Verklärte Nacht, for instance) I haven't been tempted to venture further. Other than that I think my collection is pretty wide ranging.
When it comes to opera, though I would agree that opera is meant to also be a visual experience, I love recordings for enabling me to enjoy the theatre of the mind, without the intervention of some modern producer without an ounce of musicality in his soul, who seems to think he knows better than the composer and librettist. Admittedly nothing can quite eclipse the experience of seeing a great performance, in which all the elements come together, but going to the opera is an expensive proposition these days, and a risky investment. Sometimes the investment pays off, but quite often it doesn't, so recordings will often fill that void.
My opera collection is also quite wide ranging, taking in the Bel Canto,Verdi, Berlioz, Puccini, Mozart, Wagner, Janacek, Britten, Massenet, Dvorak, Debussy, Bartok, Handel and Monteverdi. Aside from Boris Godunov and Tchaikovsky, Russian opera is (oddly, because I love Russian orchestral music) under-represented, so maybe that will be my next avenue of exploration.
Mind you, I also enjoy quite a lot of musical theatre, jazz and pop. Does enjoyment of so many different musical genres make me unusual?