A wizard also has to have that sence of mystery around and preferable talking in riddles at times, Harry does not posess any of these.
For me there is really two Gandalfs. . .Gandalf of The Hobbit and Ganalf of Lord of the Rings. . .wait! Make that tree Gandalfs as we have both the grey and the white.
I think he has more self-confident or at least is more self-praising in The Hobbit and I think that makes him even more interesting and more of a favourit character for me.