The fairest?

[Gorthaur the Cruel]

Who truly was the fairest in the Tolkien universe? Was it Varda, Melian, Luthien, Arwen, Galadriel, or Morwen?

[Raynor]

Among the Children of Eru, Luthien sits at the top of the list:
Then all memory of his pain departed from him, and he fell into an enchantment; for Luthien was the most beautiful of all the Children of Iluvatar. As for Varda, we know that:
Too great is her beauty to be declared in the words of Men or of Elves; for the light of Iluvatar lives still in her face. Given the status of the valar, I would personally go with Varda.