Lol who wants to be a troll?
wouldn't you want to be one of the Valar? They overlook everything. or the Maiar? Gandalf is a maiar.... If you don't want to be one of those godly beings, then i'd say be an eagle. They always end up saving the day... they did in silmarillion... in the hobbit, and what a surprise, they did it again in lotr.
Well hobbits and dwarves already exist, they're called midgets ...
Elves, there's actually a disease or disorder...that makes you look like an "elf" rather the myth of elf (at least in shape) stems from that disorder...
The elves of LotR are much more like the elves of the Norse, the "light elves"
Only in Norse mythology I don't think they ever came to the world of man...