Dungeons and Dragons was the best-selling RPG from 1974 to 2011. That, by itself, should speak volumes about the popularity of the game; a thirty-seven year reign at the top. But what happened? What became the best-selling RPG from 2011 to present day?
The Pathfinder RPG, published by Paizo Publishing, knocked D&D off the top of the heap. And that is an interesting story in itself.