I did not say 'failure'. That is you using that term. I said that every other fantasy RPG based off of D&D was a 'fantasy heartbreaker' and would not be as successful or as well-known as D&D.By your logic every game that doesn't outsels D&D out of the game is a failiure.
But a game can sell less and be less well-known than Dungeons & Dragons and not be a 'failure'. They are still a 'fantasy heartbreaker' because they were designed in direct response to Dungeons & Dragons, but its sales might be perfectly acceptable to the designer and thus succeed for what the designer wanted.