oldest person in middle earth

[Raynor]

In an early variant of the story, Ingwe is indeed given the title of the first elf:

Originally Posted by Of the valian tongues and its descendants, HoME V

On the march to the West the Lindar went first, and the chief house among them was the house of Ingwe, high-king of the Eldalie, and the oldest of all Elves, for he first awoke.

...although later the name of the first elf is given as Imin - in the legend of the awakening of the elves, Quendi and Eldar, HoME XI.