Zardnaar
Legend
LotR and the Hobbit are popular, but they're not D&D, and D&D doesn't try to be them.
BG3 is popular but I think CR may have the sheer weight at the moment just due to age
Look, if we want to be all in Tolkein stuff, D&D is bad at emulating Tolkein and has ever since day 1. Emulating Tolkein is going to mean Wizards are first on the chopping block, after all, and right up next are going to be Clerics. Getting rid of two of the original 4 classes doesn't sound great for emulation.
Other race options outside of the original 5 have been in this game longer than I've been alive. If they weren't popular, they wouldn't keep surviving edition after edition and being highly requested. The forerunners of Dragonborn are Draconians which have been playable since 2E, after all.
What book for playable Draconians in 2E?