The medium of tabletop RPGs is one of the strongest examples of The Network Effect outside the Internet and Telephones. The reason is obvious: a tabletop RPG is worthless without other people to play it with. This means that as soon as one specific games acquires a majority position within a marketplace it becomes very hard to disrupt, such that you have to wait for the dominant game to sabotage itself to have any chance at usurping its position.
This is why Dungeons & Dragons has remained the #1 tabletop RPG since 1974. Even its brief faltering in the late 1990s, and its stumbling in 2008, didn't really lead to its fall- and, in fact, the only real competition it has ever faced has been by its own prior editions (including Paizo's off-brand knock-off, Pathfinder).
Different genres have their own dominant games. Horror is the realm of Call of Cthulhu, and Science Fiction in general is the realm of Traveller. Shadowrun dominates cyberpunk, and mecha games start with Mechwarrior (the RPG for BattleTech) due to the dominance of the source wargame to this day. Then there's RIFTS, which is a beast to itself that dominates Kitchen Sink games. It is easier to find groups for these games than for damn near any competitor.
This is why making a tabletop RPG, if you are not one of these games, is rarely smart to do as a stand-alone product. You do them solely as adjuncts for a larger property, as self-sustaining support for the source property, in order to satisfy a secondary audience that is friendly to the source but otherwise can't engage it as they like.
Why do I say this?
Because there are levels of tabletop RPG publication that one should consider before jumping into it. The guy behind Basic Fantasy is at the hobbyist level; he makes just enough to ensure that this effort pays for itself. That's fine, and most people who do tabletop RPGs would be best off aiming for that modest level of success. This is also where those who produce playable content for an RPG adaptation of a larger media franchise ought to aim- including the big boys using big media properties.
Trying to make a profit? Now you're in for it, unless you're the one with the dominant network of users. There is only one sensible way to do this: find an empty niche, and fill it so that YOU are the dominant brand for that niche. That's how those not-fantasy RPGs got their positions. Not even Warhammer can produce an enduring tabletop RPG, and they're THE fantasy wargame brand.
Far too few get this, which is why so many try and fail to make it in this business. I've seen so many come and go that I know better than to try to roll that boulder uphill.
So, when I get around to publishing my own, I'll take the self-sustaining side-project approach. I'll do it so people who read my stuff can engage in their own adventures in my sandbox, and thereby get more out of the setting material I create for the stories and any revenue I get will be a pleasant supplement and not a necessary mission statement.