goblins are just orcs, there are different breeds of orcs (those coming from Moria etc) as there are different types of elf (orcs were originally elves that had nasty things done to them).
I could go on, and on…..
the stephen donaldson books were good but lacked the depth of history that tolkien had (if you are into that sort of thing).
it really is quite scary how much of a detailed universe and history he created, from creation onwards with countless intertwining histories of all the different races, their languages etc.
finally some disturbingly geeky suggestions on why the eagles/legolas didnt fire and forget…..
1) it would have made a shit story
2) Gandolf was a higher being, as were Sauron, Saruman, the Balrogs etc. Thw War Of the Rings was supposedly a long planned game of chess between Gandolf and Sauron, in which Gandolf could not directly use the ring, or allow it to be used by anyone/thing powerful enough to properly use it. So Elves, Eagles (which were very high animals close to the Valar (godlike beings)) were out.
3) It did kind of make poetic sense that the little hobbits overlooked by everyone, had the inner strength to remain uncorrupted…..