I know this is a bit like jumping into an argument about whether Darth Vader could defeat Batman, but here goes:
I have to agree with those that feel that the SBG/WOTR game mechanics do not scale well to represent the power and majesty of the First Age characters of the Silmarillion. Here's why:
Looking at the whole history of Middle Earth, there is (to me) a continuous, linear change from the world being shaped by primeval, numinous powers in the beginning, to the major forces in Middle Earth being more mundane and numerous. By the end of the Third Age, even before the One Ring is destroyed, the Elves are in decline everywhere. Even by the time of the arrival of the Istari to Middle Earth, the only remaining bastions of the original power of the Elves are where there is a Ring of Power: The Grey Havens, The Last Homely House, and Lothlorien. Even the forces of evil decline through the ages, with the First Age being dominated by a corrupted Vala (Melkor/Morgoth), to the original incarnation of Sauron, who was able to bend an elf like Celebrimbor (who may have even seen the light of the Two Trees - the record is not clear) to his will. Eventually, even Edain can see Sauron for what he is, and he is defeated the second time by a force of mere Elves and Men (remember, he's a full Maia).
Along with the decline of the powers of Middle Earth through the ages, there is a subtle but important periodic change in the structure of the world: Valinor moves further and further away from Middle Earth proper, and becomes harder and harder to reach. Eru and the Valar (good band name) create and guide Middle Earth, and some of them even reside there, in the beginning. With the awakening of the Firstborn, the Valar retreat to Valinor, and then Valinor itself successively retreats through the ages.
To me, it's a central theme of the books: Now it is time for the age of Men. It doesn't read like unbridled epic forces for three ages and then suddenly it's just men. Rather, there is a clear and gradual decline from the supernatural to the mundane.
In my mind, Feanor could take on Elrond (who is only half elven), Galadriel, Celeborn, Cirdan, and Thranduil all at once without breaking a sweat.
And Darth Vader would totally defeat Batman.
