Who was the greatest Elf?

[Legolas]

Who together with the greatest of all the Eldar, Lúthien Tinúviel, daughter of Elu Thingol, are the chief matter of the legends and histories of the Elves.

Thus, you can no longer argue over the matter. Tolkien explicitly stated who the greatest elf was.

If such debates interest you, perhaps you could ponder the question of who the coolest elf is, or something like that.