I've known the standard operas backwards and forwards for many years, so most of my complete opera recordings are of really interesting rarities such as
Padmavati by Roussel,Enescu's Oedipe, Nielsen's Saul and David, Schreker's Der Ferne Klang(The distant sound), Notre Dame by Franz Schmidt, based on the famous Victor Hugo novel the Hunchback of Notre Dame, Dvorak's Armida, The Devil and Kate, Smetana's The Kiss, Libushe,
and The Devil's Wall, Krenek's Jonny Spielt Auf, The Birds by Walter Braunfels, The Charlatan by Pavel Haas, Flammen by Erwin Schulhoff,Francesca Da Rimini by Riccardo Zandonai,
the less familiar Richard Strauss operas Intermezzo, Die Liebe der Danae,Friedenstag,
and The Egyptian Helen, Gluck's Armide, Handel's Riccardo Primo, Janacek's Excursions of Mr. Broucek and Osud(Fate), Catalani's La Wally, Tiefland by Eugene D'Albert, Pfitzner's Palestrina,
Rossini's Il Signor Bruschino , Nixon in China by John Adams, Undine by Albert Lortzing,
Der Vampyr (Yes a vampire opera !) by Heinrich Marschner, Mozart's Lucio Silla,
Mazeppa by Tchaikovsky, The Gambler and Semyon Kotko by Prokofiev, and the Fiery Angel,
The Demon by Anton Rubinstein, and the Rimsky-Korsakov operas Sadko, Kashchei the Immortal,
The Maid of Pskov, and The Legend of the Invisible City of Kitezh.
I also have the Levine/DG/Met Ring complete in one convenient set, the classic Furtwangler/Flagstad Tristan&Isolde, Fricsay's Flying Dutchman on DG, the La Scala Ring with Furtwangler, and several other standard operas.
I also have the Vox set of the original version of Madama Butterly,which includes all the music
left out of the familiar version.
Lots of cool operatic stuff.