A much better English than mine would be needed to start this problematic topic.
We have tested the vitality (or lack) of the symphony (and the "concept" itself) in the last fifty years (and the discussion is going on).
So, taking again as starting-point the year 1960, which are according to you the best (not simply your favourites) three operas of the past fifty years, sung or unsung (with short reasons)?
My list would be:
-B.Britten "Death in Venice". Masterful (but a bit over-intellectual) culmination of a great operatic (and not only) composer (here however less overtly and less successfully theatrical than in several earlier operas);
-John Adams "The Death of Klinghoffer". New and fresh blood injected into the opera. Nothing over-intellectual. Direct communication; masterful craftmanship; real theatricality.
-O.Messiaen "Saint Francois". Great "vision", nobilty and mastership (by a great composer not really showing theatrical istinct).
I have taken in consideration the most disparaged composers (by whom I know, in some way -maybe insufficiently, at least one opera in the period concerned: Adès, Nyman, Daugherty, Bolcom, Schnittke, Berio, Nono, Maderna, Menotti, Rota, Barber, Tippett, Henze, Birtwistle, Bernstein, Penderecky, P.Glass, Reich, Stokhausen).
Not considered (as I don't know any of their operas, and I would) Rautavaara, Tubin, Weinberg, Schedrin, Corigliano, Harbison, Adamo, Heggie, Landowsky.
Of course not considered a lot of others (possibly worthy).
This is one category which is unrepresented in my collection. I'm afraid that my most recent operas are Tippett's Midsummer Marriage and Barber's Vanessa. Wonder why?
Tippett's 'King Priam' just squeezes in, and is a great favourite of mine: the libretto, though Tippett's, has the advantage of being based on someone else's story: the music perfectly suits the action. I'd defininitely include 'Death in Venice', a masterpiece. For more recent ones, Birtwistle's 'Minotaur' impressed me a lot, and James Macmillan's 'The Sacrifice', even though they cover stories already dealt with by Tovey and Holbrooke respectively. The Macmillan had me so gripped when listening one day recently that I missed my station to get off the train.
I can offer up a couple of American operas which I think should be better known.
John Adams: I'd choose Nixon in China instead of Klinghoffer. It doesn't entirely work, but the concept is phenomenal, and there are many very powerful moments. It's a very impressive score which I love to revisit from time to time.
Robert Ward: The Crucible. (Just squeaks by, as it was premiered in 1961.) I can't speak to its importance on the world stage, but it's perhaps my favorite under-loved American opera. Very, very powerful...and there's a good deal of excellent ensemble writing, as well as some fine solo passages.
Andre Previn: A Streetcar Named Desire. Excellent work - I saw it in Washington some years back, and was completely blown away. Why it isn't done more often I'll never understand.
I can probably think of a few more, once I get my brain in order. :)
Not having taken in consideration Previn's "A streetcar named desire" was my carelessness. Indeed I attended a performance in Torino some years ago (it was up now the only Italian staging) and appreciated a lot. That would rank high in my list (even if not in top three). Now I would listen and see (I would a DVD) Previn later "Brief encounter".
"Nixon in China" was for me alternative as one of top choices to "The Death of Klinghoffer".
One favourite for me (I couldn't say a "great" opera) would be "Jackie O." by Michael Daugherty.
I really enjoyed Ligeti's "La Grande Macabre" when it was done by ENO. Also "The King Goes Forth To France" by Aulis Sallinen; and I must admit to a soft spot for Philip Glass's "Akhnaten".
One that I really enjoy is Lorin Maazel's 1984. Love the book, certainly. But the opera really brings a harrowing sense of reality. Probably won't ever get a hearing again unless Maazel does it, but at least the DVD captured it well.
Operas by composers like Daniel Catán and Curtis Bryant fall squarely withing the tradition extending from Mozart to Strauss, Prokofiev, Britten, and Barber.