What's interesting with D&D 5 is the return of Third Party Publishers. Frog God Games has made it into our top ten with their D&D 5 and Pathfinder compatible products. Really, it's about their D&D 5, especially Fifth Edition Foes, an excellent monster book that's D&D 5 compatible. Their similar Pathfinder books sell far fewer copies than nearly identical D&D 5 books. But what about the D20 glut, you ask? Isn't third party publishing for D&D dead?
As long as Wizards of the Coast keeps people hungry for new content with their trickle release schedule with D&D 5, The Stable IP Edition, there will be demand for 5E content. Coming in at #9 is Gale Force Nine with their D&D 5 spell cards (which would be higher with a steady supply), and Goodman Games at #19 with their D&D 5 adventures.
Adventures never sell well, so no surprise there. Figure one in five players (the DM) could potentially buy a published adventure and only half of them actually do (10% of the market).
Licensing (or lack thereof) is a whole other discussion. GF9 sells licensed D&D products, while the others do not.
Note "Other" in the third position. D&D, Pathfinder, and compatible lines may be 70% of sales, but we carry about 25 additional brands in the Other category, for about 45 total "lines." A line can be a single book, so this can include a lot of things.