A.C. Douglas points us to this article, which I didn't see the first time 'round, but wish that I had. It is, indeed, a very nice exploration of Wagner's most (to me, anyway) elusive music-drama: Parsifal. This passage, in particular, I like:
Shall we tread carefully then? Heck no: he didn't. Let's do The Master proud, and declare Parsifal, the "stage-consecration festival drama" that he composed specifically for the theatre he designed at Bayreuth, and the work widely performed throughout the German-speaking world at Easter, to be the most extraordinary single achievement in opera.
Not the greatest opera, note, though it must be a contender for that non-existent honour, along with at least four of his other works. No, the most extraordinary - in its conception, sound, influence and history. Ever since Nietzsche called it "a work of perfidy, of vindictiveness", this opera of redemption, Wagner's "farewell to the world", has been loved and mistrusted in a way that is unique.That's my idea of really incisive analysis. I might say, though, that the entirety of Der Ring des Nibelungen trumps Parsifal for the "most extraordinary single achievement in opera." Wagner would detest the term "opera" applied to any of his mature works (i.e., post-Rienzi), but I'll beg his forgiveness. Furthermore, the idea that Der Ring is a multiple achievement is attractive, but it is one story with one set of characters. I'll argue that it is a single work, and it is certainly the most monumental achievement ever conceived for the stage - and it might be the single grandest in all of art; however, there are some buildings (San Marco, Hagia Sophia, and Chartres) that might trump it - but that's another debate.
Of course, if Wagner had written one - and only one - of his major mature works, he would be considered no less a master. Such was Wagner.
Edit: A.C. Douglas suggests changing "post-Rienzi" to "post-Lohengrin." That's probably correct (in fact, it is correct), but I still see Holländer as the moment when Richard Wagner became "Wagner." So, I'll just append this note and let my readers, such as they are, decide for themselves.