Wasn't Eärendil a mortal man? So why would he be most beloved to Elves?
Earendil was half-Elven, who chose to be an Elf.
Why would his star have been particularly beloved?
- It was actually one of the Silmarils, the last true light of the Two Trees of Valinor, which the Noldor had fought and died to recover.
- It was a sign from the Valar: after hundreds of years of despair and defeat against Morgoth, the Star of Earendil was a symbol that the Valar (and Eru) were still with them, and a reminder of the War of Wrath in which Morgoth was utterly defeated and the Elves freed from his domination of Middle-Earth.