Underrated songs by legendary bands and artists

Yes, I'm sure at least a good number of you know of bands with great tunes that just haven't hit the big time yet, or perhaps never will. That, however, is not what this thread is for. Instead, we're going to look at songs from the gods of their respective genres that- sometimes bafflingly- slipped through the cracks of the zeitgeist and perhaps even a large portion of the fanbase. (Though other times there are very good reasons, like one that's released before the people behind it became popular.)
So… yeah. Go crazy

As the resident Pink Floyd fanatic, I knew my selection would have to come from them. Originally I was set on selecting a track from Meddle, but I decided later to take a step backwards into obscurity. Ladies and gentlemen, Roger Water's If from Atom Heart Mother.

Man is this a hard one to put into words.

Well first of all, Roger Waters and David Gilmour are pointing and laughing at most modern-day artists' attempts at pulling off the simple vocal/acoustic guitar pairing without coming across as total douchebags. In my opinion, it's never sounded more sincere than right here. Of course these guys know to add more, and they do, including sound effects (of course, it's Pink motherfucking Floyd) and one of the most bizarre, and yet strangely wonderful and perfectly fitting, electric guitar solos of all time.
As for the lyrics… also very minimalist. I would describe them as stream-of-consciousness, like when you're alone in your home or walking down the street, and out of nowhere you begin to ponder your life. (I don't know if this is is a weird thing to do, but I know I have on occasion, especially when I'm standing by myself in the cold around dawn or dusk.) In this case, the statements, all in the form of conditional sentences, come out of the mind of a man who's both sad and disappointed with himself and a bit unhinged, which certainly describes ol' Roger at times. This was before he got the near-consistent job of penning the lyrics for Floyd, and in his own very, very strange way he showed off his chops here.
Overall, this is one of those songs that more than likely never could get popular. And I love it, both despite of, and because of, that fact.