I was discussing the scene in the movie when Gandalf and Elrond were talking in Rivendell. Elrond seems to scoff at the idea of men being strong enough to protect the Ring. He recounts in flashback how Isildur was too weak (and greedy) to destroy the Ring at the time of the battle where Isildur cut the ring from Sauron's hand. I'm not sure in which book this information may be found.
Looking at the examples of the leadership of men at the time Elrond made that statement what is there to disagree with? Theodin and Denethor are both sitting on their fanny's waiting for the end. Saruman and Sauron have both under their thumbs. Without the Hobbits to help Aragorn tip the balance where would men be?