Elves are beautiful, long-lived, skillful, perceptive, magical. In Tolkien's work, they are Humans++, and pretty much everyone knows it, but they have to migrate to a legacy server because version updates have deprecated core parts of their code.
And it's worth noting the other two races that have risen up to potentially threaten the Human-Half-elf-Elf triune complex: tiefling and dragonborn. Two races both featuring a blend of human-like traits and traits associated with a powerful, dangerous, charismatic otherworldly creature. Neither one of them actually has threatened it. But the potential remains for such a thing to occur, especially given the clear trend of rising popularity for dragonborn.
Honestly, though, we don't even really need anything more than the beauty angle. Stereotypically "beautiful" characters are just straight-up more common than other archetypes. You see it most plainly in, for example, the incredibly lopsided distribution of races in World of Warcraft's Horde after the Burning Crusade expansion came out: almost everyone wants to be a Blood Elf, because Blood Elves are Horde members that are pretty.
You can't fight evil if you don't look cute.
