I think the great things about Link are sometimes indescribable.
He is full of courage, strength, selflessness, optimism, kindness, and like most people said, even though he is everything that may not seem humanly possible to be, he is human.
Though these characters aren't real, they make them seem really realistic to talk about them. That's one thing I like about the characters in the games ( besides the freaky, sick monsters in most): They're life-like enough for people to want to look up to them.
In all, I find that the greatest thing about Link is that he is the human no one has or will ever be (well, so far anyway...).
PS: You know Cloud in Final Fantasy??? He looks a wee bit like a girl, to me. His face is a bit too gentle for a Japanese sword-fighter who almost never dies, unlike Link. Not only does Link fall but somehow manages to get back up, he has a hero face and that sense of purpose.