Zardnaar
Legend
Though it is worth noting that the instant you could play a Horde elf, they became the most-popular playable race in the game, bar none except perhaps human.
People like playing beautiful "bad" boys/girls. Blood elf gave players all the "savage Horde, we do what we want, we respect no law but force" stuff they craved, while still getting to be traditionally attractive. Even having blatantly overpowered alternatives (e.g. draenei back in BC) didn't dent the tide of blood elves.
AKA Drow effect.
Elves are generally peettier/better humans. Evil ones maximum emo powah!!!!