Both pieces, and some of the comments, are worth reading.
Here are my scant shekels on the topic:
Truly, Weingrad does miss the obvious huge contributions to the worlds of fantasy made by Jews - not the least of which is the huge Jewish population in writing for role-playing games in fantasy settings (Weingrad mentions how Israelis play D&D but misses the essential Jewish contributions to the genre).
Many have already commented that the notion that there "should" be a Jewish equivalent to Narnia seems a little silly. Jewish culture is inherently skeptical, so idealized worlds without dark underbellies ring hollow to a Jewish ear. Meanwhile Jews do seem to aim for a utopian ideal, but understand that aiming there doesn't mean achieving it is reasonable or around the corner.
Furthermore, Jewish ideas about messiah and a vision of the way things "should" be are so diverse, because of Judaism's embrace of dissent, that identifying a story, like Narnia, as representing "the" Jewish perspective, as opposed to merely a "perspective influenced by Judaism," may be a truly fruitless effort.