Superman's roots are undeniably Jewish.
The co-creators of Superman, Jerry Siegal and Joe Shuster are both ethnically Jewish, although according to Gerard Jones' excellent history of the origin of superhero comics, The Men of Tomorrow, neither were relegious. Likewise, Harry Donnefield, the founder and first president of DC. Even Donnefield's sometime accountant sometime vice-president Jack Liebowitz was Jewish. All of these people were secular Jews and Siegal and Shuster disavowed or downplayed any influence of relgious Judaism on their works.
Siegal and Shuster's first Superman was in a short story written by Siegal and illustrated by Shuster. This story, titled The Reign of the Superman features a scientifically enhanced Nietzschian superman who reaks havok before being finally overcome. In 1933, as Hitler ascended to power in Germany, calling himself the Nietzschian superman, Siegal and Shuster re-imagined Superman as a hero.
It may be a coincidence that the two Jewish young men's creation of a heroic superman coincided with Hitler's rise, or it may not. Regardless, Shuster and Siegal's creation eventually sold, and in popular consciousness the Superman was forever linked with protecting the weak, instead of with the use of power to dominate and destroy the weak.
Superman is the ultimate immigrant: he comes from some other place, and lands in America. He masquarades as one of them, but at his core he isn't. As Clark Kent he seems meek and weak and easily pushed around, but behind his secret identity he is a powerful warrior for good. He's not an American, but he fights for the American Way.
Even deeper than the political symbolism is the religious symbolism of Superman. Superman is rooted firmly in the talmadic injuction to do good for its own sake. He is, in short, a very Jewish superman, and his strength comes with a moral compass.
Kal-El's arrival in a basket is strongly reminiscent of Moses' appearance in a basket in Exodus. The Exodus is the central story of the Torah, and its most significant instance of salvation. As such, Moses is the most important saviour in the story of Israel. Superman is a Moses figure in more than his appearance as a baby in a basket, but also in that he is a saviour, whether that means in his very person symbolically saving Krypton from complete extinction, or saving an man from being wrongfully executed for a crime he didn't commit, as he did in his very first appearance. For much of his history, and especially in his original incarnation, Superman spent more of his time protecting the innocent than fighting supervillains.
Yet since Moses is a prophetic precurser of the Messiah, Superman is also a Messiah figure. He is a Messiah figure even before he is a Christ figure. This distinction requires some clarification.
Though as most Christians and Jews already know, "Christ" (Greek) and "Messiah" (Hebrew) both mean "Annointed One", the terms are, especially for Jews, not synonomous. I use "Christ" to refer to Jesus of Nazareth, but "Messiah" to refer to the promised savour of the Jews. As a Christian myself, I believe that Jesus is the Jewish Messiah, but a distinction is still helpful.
But Superman is a Messiah figure even before he is a Christ figure. He represents the Jewish eschatological hope of salvation, the hope of God's intervention, the hope that things will not always be as they are now. Superman symbolises the Jewish conviction that the world can be better than this.
Superman is often accused of being adolescent wish-fulfillment in action: a super-strong hyper-masculine muscleman created by two geeks, a bullet-proof man created by Jerry Siegal, whose father was shot dead by a petty thief. He is all of this. But even more than this, Superman, despite Siegal and Shuster's supposed secularism, is a Jewish messiah figure--a personification of the hope of Judaism. He is a protector of the weak and champion of good in a world with too much evil.