Ramathilis' question is of course an INTERESTING one, but my observation is that I come from an era of D&D (the early days, I started playing when Blackmoor was released or thereabouts, and my DMing really started with Holmes Basic) when there was almost no canon. Not only was there not canon but the attitude of those days was that canon was BS. The mark of a real serious DM was to create everything from whole cloth. Sure, you probably used the more typical canonical monsters, orcs, dragons, whatever by default as they were in the Monsters and Treasure book, but nobody could make up EVERYTHING. The whole book only had about 50 monsters in it anyway, and they were kinda vaguely defined.
So, NO! @
RAmathilis, D&D FOR ME is contrariwise not at all all of this detailed lore which was in any case grafted MUCH MUCH MUCH later in the history of the game, a dozen years after our playstyle and attitudes were set. All the 2e piling up of lore and settings and whatnot? To our group it was sort of puzzling, why spend your money buying OTHER PEOPLE'S lore??!! The idea was to be judged on the creativity and interest of YOUR lore and to validate it and flesh it out with play. Our group spent a dozen years trying to understand the workings of The Mountain and why the fate of heroes was always tied to walking one mountain path. It was COOL. Yeah, there were dragons and liches and beholders and whatever in that campaign and a LOT of that material was drawn at least partly from other D&D sources, but that DM wasn't going to drop stuff on you a certain way because it came out of a book, and if someone said "but a Succubus isn't a Devil, that can't happen, that's wrong!" we'd have all been like "WTF? What's he on about?"
I mean I can look at all the FR stuff Ed Greenwood did and that other people did and its like "Cool! They did a lot of neato stuff", but its not any more "correct" or deserves any more respect or pride of place than any other lore anyone else made up just because TSR printed it.