Richard Strauss' 'Morgen'. The most beautiful song in history? Check out Barbara Bonney's recording.
Certainly one of them - I enjoy the Last Four Songs as well. So far I have Felicity Lott - I love the combination of the Songs with the Orchestral pieces by Jarvi on Chandos - one orchestral piece by Strauss is enuf and Lotts singing is just rapturous. I've got Schwarzkopf and Szell on EMI and Isokoski on Odine. I prefer the former.

Now the $64 question - am I missing anything if I don't hear Bonney? I'm really not familar with her voice.
Don't know Isokoski. Lott and Schwarzkopf are both fantastic, but very much in the 'old diva' style. I haven't heard those particular recordings, but Bonney's version is simple and lush. I would guess that the other two are not, but I could be wrong. That's not a knock on them, I'm just guessing that it's a completely different style.
My best version? O.K., it's unobtanium AFAIK, but here it is, since you asked.

Very politically incorrect. I have a BASF vinyl recording of Roberta Peters(!) with Leonard Hokanson at the 'Flugel' (piano). Unbelievable, and you really need someone with the right touch/sensibility at the piano. This is it. If anybody knows of this on CD, please let me know. Copyright is 1972.