Unpopular/niche RPGs can be found on just about any game system, and if they're both unpopular and unheard of, they probably only sell a couple hundred thousands copies as opposed to the millions of a more heard of games.
I think that the majority of these unpopular/niche RPGs are pretty good games. I want to play them, however I generally don't because I'm afraid the game will involve some backstory I don't understand or will just be another faceless game - while such a game is worth a try in my opinion, it's not worth paying the same price as a more popular game over. So I save time by not playing them, but possibly miss out on a few good games due to my cynicism of not easily believing that an unpopular game might be good and worth buying.
I think that the majority of these unpopular/niche RPGs are pretty good games. I want to play them, however I generally don't because I'm afraid the game will involve some backstory I don't understand or will just be another faceless game - while such a game is worth a try in my opinion, it's not worth paying the same price as a more popular game over. So I save time by not playing them, but possibly miss out on a few good games due to my cynicism of not easily believing that an unpopular game might be good and worth buying.