Here is a Buzzfeed quiz about what operas out of a list of 100 you have seen. [Originally from 2015.]
Out of the list, I was in:
The Marriage of Figaro (Mozart)
Die Fledermaus (Strauss)
Hansel and Gretel (Humperdinck)
Salome (Richard Strauss)
The Queen of Spades (Tchaikovsky)
The Force of Destiny (Verdi)
Death in Venice (Britten)
The Bartered Bride (Smetana)
Out of what remains, I have not seen at all:
Akhnaten (Philip Glass)
Albert Herring (Britten)
Operas that I have seen only in HD from the Met:
Maria Stuarda (Donizetti)
Operas I have seen only on DVD:
The Fairy Queen (Purcell)
Written on Skin (George Benjamin)
Anna Nicole (Mark Anthony Turnage)
The Minotaur (Harrison Birtwistle)
The Coronation of Poppea (Monteverdi)
Benvenuto Cellini (Berlioz)
The Silken Ladder (Rossini) (La Scala di Seta, I have an unwatched dvd.)
That makes 88 live, 3 HD only, 6 DVD only and 4 not at all. I think that's pretty good. The list comes from the ENO and emphasizes their repertoire.
Edited end of 2018 I find that Akhnaten and Gloriana are the only ones I have still not seen.
Edited again in August, 2020, I find that Gloriana is the only one I haven't seen. Perhaps it will never play here. I am pleased to say that today I watched and very much enjoyed Britten's Gloriana. That makes 88 live, 3 HD only, 6 DVD only and 0 not at all.
I see the list is still in place, so compile your own.