It's no secret that Nietzsche liked Wagner, then turned on him rather nastily:

Wagner represents a great corruption of music. He has guessed that it is a means to excite weary nerves—and with that he has made music sick. His inventiveness is not inconsiderable in the art of goading again those who are weariest, calling back into life those who are half dead. He is a master of hypnotic tricks, he manages to throw down the strongest like bulls. Wagner's success—his success with nerves and consequently women—has turned the whole world of ambitious musicians into disciples of his secret art. And not only the ambitious, the clever, too.— Only sick music makes money today; our big theaters subsist on Wagner.

--Der Fall Wagner

But what I hadn't known was that despite Nietzsche's rather...intemperate attitude towards Christianity--

I call Christianity the one great curse, the one enormous and innermost perversion, the one great instinct of revenge, for which no means are too venomous, too underhand, too underground and too petty - I call it the one immortal blemish of mankind.

--Twilight of the Idols

--he could not remain unmoved by Wagner's most directly Christian opera (despite anyone's maunderings about Buddhism and Schoepenhauer), Parsifal. As he wrote to his sister:

I cannot think of it [the overture to Parsifal] without feeling violently shaken, so elevated was I by it, so deeply moved. It was as if someone were speaking to me again after many years, about the problems that disturb me - naturally not supplying the answers I would give, but the Christian answer, which, after all, has been the answer of stronger souls than the last two centuries of our era have produced. When listening to this music one lays Protestantism aside as a misunderstanding - and also, I will not deny it, other really good music, which I have at other times heard and loved, seems, as against this, a misunderstanding!

One wonders how much of Nietzsche's dislike of Wagner was driven by envy (and this despite one's firm conviction that psychological motives ought never to be ascribed to anyone, no matter how deserving). After all, Wagner had the woman and the life that Nietzsche wanted, and moreover, Nietzsche's "Nachklang einer Sylvesternacht" reduced Wagner not to ecstasy but to derisive laughter. All of which was a rather composed (rim shot!) response compared with Hans von Bülow's declaration that Nietzsche's work was equivalent to raping Euterpe.

Each fellow arrived at immortality in the end: Wagner through his music and Nietzsche through his philosophy (and thank Heaven it wasn't the other way 'round!). It just seems that Wagner enjoyed the trip so much more.