Similarities between the roles of the Valar and the Eldar

[Lord of Angmar]

It would seem that this is simply the natural 'flow' of Arda as laid out by Iluvatar. The Valar's job it was to watch after Ea before the Coming of the Firstborn. The Valar took it upon themselves to nurture the Elves by bringing them to Valinor with - ahem- mixed and questionable results. The Elves then received the task, as you said, of preparing the world for the Secondborn, the Atani - Men. There are similarities in that the Valar had a shaky relationship with many of the Elves (the Noldor, obviously, in particular) while ever remaining the close friends of others (the Teleri and the Vanyar). Similarly, the Elves maintained good relations with many of their successors (the Three Houses of the Edain and later the Elendili) while being on entirely bad (or nonexistent) terms with many others (the lesser Men of Middle-earth, Ar-Pharazon's Numenoreans, etc.).

I cannot see any other major similarities along those lines (at the moment).