Why does Gandalf have the third elf ring?

[Balin999]

i dont think that saruman was ever greater than gandalf at all, and that is was percieved that he was. but then again, saruman came from the same guy who made sauron

Saruman was greater than Gandalf, because he was the "White". For example, Gandalf asks him for council in the matter of the ring and respects him very much.
Second, Saruman was Head of the White Council (allthough Galadriel wanted Gandalf to be head/chief, whatever).
After Gandalf is revived and returns to Middle-Earth, he is Gandalf the White and brakes Saruman's staff and commands him to come back to his window. He even says that he is in a way Saruman, and he is more powerful than before, so that clearly points out that Saruman was (in the beginning of the story) "greater" or wiser/mightier than Gandalf.