At least with D&D you have a bazillion campaign settings, retroclones, 3pp, etc that all take their own spins on rules and fantasy tropes.
I can't recall off of the top of my head here a single fantasy RPG that has any kind of real traction in the hobby that is not d20 based outside of WFRP.
I guess technically there's also RQ. But Glorantha.
Fundamentally, it's all still D&D.
The bazillion campaign settings and clones are just D&D gamers honing in to their "perfect" flavor of D&D.
... There a huge conceptual space that can be explored here, so I'm astonished that there's just one game with one campaign setting (with several decades of unavoidable canon/lore baggage) that dominates 99% of the available scene....
I'm not.
First mover status in RPG land is HUGE. H.U.G.E.
As in - Very Big.
Every commercially viable niche in RPG land has already been taken.
Fantasy:
D&D - once the 800lb. gorilla in the room. Now the 80,000lb. King Kong of the hobby...
Pathfinder 1-2e - Clone D&D is now the perennial #2 RPG.
OSR - more D&D.
Basically, the wider hobby has doubled down on D&D fantasy RPG's to service their roleplaying needs.
The alternate go-to games: RQ, and WFRP, are no where near as prominent in the hobby as they once were.
Horror:
CoC, still. Unchallenged for decades.
Vampire/WoD - mismanaged into also-ran status, but still the only other 'go-to'. No viable contenders to take its spot have surfaced.
Straight up Zero contenders. No one is even really trying. Kinda odd actually...
Sci-Fi:
Traveller, still a loyal following. Small, but loyal.
Star Wars. Whomever has the license to this IP dominates over everything else in Sci-Fi. Until they lose it, then the next IP holder gets to sell a Star Wars RPG and dominate Sci-Fi RPG sales.
The rest is a bunch of niche systems in *
Thunderdome Mode.
Cyberpunk:
Cyperpunk, still. Red is the current version.
Shadowrun - usually a go-to, but currently in the process of being mismanaged into also-ran status. No contenders to take its spot have risen yet.
Some alternate systems have popped up in the past few years, and there might be traction there if one can break out of
*Thunderdome Mode.
IMHO Both SR and CP are vulnerable to this.
Superheroes:
Mutants and Masterminds is really the only known "name" go-to RPG.
Almost a fallen genre. Champions ceded it's first mover status years ago. It's practically a Footnote in RPG history at this point, and no current game has risen to be 'The' Supers RPG everyone is trying out.
It's mostly just niche systems in
*Thunderdome Mode, for now.
Alt-Universe quasi-historical Fantasy:
Seventh Sea & Legend of the Five Rings used to be a thing. Both now firmly mismanaged into also-ran status. There are other games out there, but no one cares.
A fallen genre bordering on dead.
Post-Apocalyptic:
We had Gamma World, Twilight 2000, Aftermath... There is stuff out there now, but people seem to be getting their Post-apoc genre fix from CRPG's these days, so no one has shown up to be "that game".
A fallen genre. And no, 2d20 Fallout will not revive it...
Modern:
A fallen genre IMHO. Stuff like Top Secret and James bond used to be more prominent, and d20 modern was a thing for a bit. But now it's all kinda just a big 'meh of niche RPG's that can't be tossed to enter
*Thunderdome Mode.
Western:
We used to have Boot Hill and Deadlands used to be a thing. Another fallen genre bordering on dead.
Generic/"Universal" systems:
Honestly I feel that the generic system has more or less gone by the wayside. GURPS and HERO are essentially dead stick in the hobby. I feel that the OGL was the reason for this. Most people want a version of a game they like. So why bother having to curate a tome like gurps or hero, when a d20 based game or the SRD gets you 80% to where you want to go, and you can just homebrew the rest.
And none of your players have to "learn new rules"...
The OGL is still killing it. You see that with modern publishers putting out 5e versions of their games that had dedicated systems.
The Rest:
Yes, there were some one-hit-wonder games that have since fallen by the wayside. Some I really liked, but ultimately inconsequential. Just like there are one-hit-wonder games now that will ultimately meet the same fate.
The real problem contenders have is that "First Mover" status in RPG land is so huge that people still love their established RPG IP, and are completely uncurious about looking for anything else; even if the IP is borderline dead.
The economics of the RPG hobby have also changed since the 90's. Making it significantly harder financially to breakout and unseat an established RPG IP with a fully supported game line. And that is assuming the game design side of your operation is solid.
The real issue would-be contenders have is that people like to play "supported" game lines. It is not enough to have a competent core game. You will need to release 3-4 adventures/supplements a year on top of that.
Vampire: The Masquerade released 12 supplements in its
first two years of introduction. Outside of Pazio who in RPG land is replicating that today? (Although 5e has shown that one does not need hit the splat treadmill that hard - hence my 3-4 supplements per year.)
Which shows the other advantage that established RPG IP have: Their back catalogs...
You want to create an urban fantasy game that isn't World of Darkness? That people will actually buy? You either need to have a Killer great idea hook that will attract new players to your urban fantasy game.
Or, you need to tap into a pre-existing player base by making a clone that won’t get you sued into oblivion, and get enough of them to move over to your new hotness fully supported system to eventually supplant the older RPG IP's player network.
My advice: Don't go head to head with CoC...
*Thunderdome Mode: My catchall for all the more or less unknown games competing with each other in their respective niche gaming circles for attention from the wider hobby.
