Admittedly it is unlikely that somebody reading this blog is unaware of what a role-playing game is. Nevertheless I can recommend this PBS mini-documentary on YouTube about what Dungeons & Dragons is, and how it influenced culture over the last 30+ years. The documentary argues that the success of a game like World of Warcraft would not have been possible without Dungeons & Dragons having introduced so many people to the idea that playing a dwarven warrior or elven wizard might be fun.
But if MMORPGs are the children of D&D, they can be accused of patricide. Although I would say that the experience of playing that elven wizard in an online game is in many ways inferior to playing one in a pen & paper roleplaying game, and is missing much of the interactive storytelling, fact is that an online game is a lot more convenient than a pen & paper game. You can play solo, at any time outside the maintenance window. Even the most complicated feat of organization of a MMORPG, a raid at which everybody has to be there at the same time for a block of several consecutive hours, is easier to organize than the most basic organization of a game of Dungeons & Dragons, where in addition everybody needs to be at the same location.
While Dungeosn & Dragons and other pen & paper systems are far from being dead, they are obviously way past their prime. Hobby stores selling role-playing games, board games, and card games are an endangered species, and only a part of that is due to online distribution. While impossible to measure, I'd guess that there are less people playing Dungeons & Dragons today than 10 or 20 years ago. People adopted MMORPGs as substitute and abandoned the less practical pen & paper game, in spite of it offering a much higher degree of freedom and better social interaction. That's a shame.