I’m about to say something I personally find fascinating…
I think the chances are pretty high that at least 70% of all media ever created are obscure/forgotten. It’s all about publicity usually, only occasionally does a piece of media reach fame, and that’s usually because of some form of publicity. Take Klaatu for example. Their solid debut album was only well known because they were at one point literally thought to have been a Beatles reunion. Before that, they fell into obscurity not long after they released it (yet were still critically acclaimed).
I’ve also seen (and bought) some old movies only available on one compilation DVD, the same goes for some old songs as well, I’ve seen (and bought) some genuinely great (and very old) songs only available on one compilation album, some you can’t even listen/watch ANY part of the song/film at all without buying the CD/DVD first, making it a bit of a gamble some of the time.
Now, there are a lot of silent films available to the public, but there are estimates that 90% of all silent films are now gone. If the majority of all silent films ever made no longer exist yet there is still a behemoth of silent film that do still exist, that must mean that the vast majority of say, '80s movies are obscure.
On top of that, I’ve seen some films that are incredibly hard to find yet still exist, and very rarely some foreign films that aren’t even on IMDb at all, yet are on some foreign equivalent (such as Douban).
And I bet those super obscure songs, movies, and maybe even TV shows must be hiding some great surprises, such as one very obscure album I recently bought.