The Aslan comparison is apt. Aslan is Lewis’s Christ character. As he tells us at the end of Dawn Treader that in the children’s world Aslan goes by another name, and he brought the children to Naria so that “by knowing me here, you might know me better there.”
As for the nice guy bit, that doesn’t fit. Lewis again, different book, “This man we are talking about either was (and is) just what He said or else a lunatic, or something worse.” Kind and great human teacher just isn’t a option for the man who when around claiming to be the Son of God.