I love the Chronicles of Narnia. I've read them myself, I've read them with my wife, I've read them to my children. We own DVDs of the BBC productions of four of the novels. A drawing of Aslan flying with Lucy and Susan is currently the background image on my computer display.
But: The identification of Aslan and Jesus does not bear much scrutiny, either artistically or theologically.
And: In particular, the "Deeper Magic From Before the Beginning of Time" bit is very bad art, and worse theology.
Notwithstanding: The fact that many people love Aslan and don't merely overlook the bad art, but actually insist it is good art, because (I suggest) they regard Aslan as Jesus, know what Jesus did for us, and supply what is wanting in Lewis's story from their own hearts.
However: I do grant that the "not a tame lion" line is excellent.