It is hard to see Superman with some kind of religious connotation. The God-like savior from a distant world, sent to Earth to hear our cries for help and protect us from harm. He answers all our prayers and delivers us from evil. It is a role that is hard for the Man of Steel to shirk, as it is practically built into his DNA as a superhero. Even among other heroes, he stands as something of a God. He is the All-Father whose very creation was the Big Bang of the entire genre.
In Superman #659, we meet an elderly black woman who lives in Suicide Slums, a very bad spot in Metropolis, who begins to believe that Superman is her very own guardian angel. Whenever she sees crime being committed, she engages the perpetrators, putting herself in jeopardy until Superman arrives to intervene. In her mind, Superman is only a prayer away at all times, until one day, when a fight with a larger than life monster prevents him from getting there in time. The woman sustains a minor injury. Later, as Superman is visiting her, she assures him that it was not his fault that she was injured and that while he was not there to save her, the problem worked itself out in a fitting manor, showing that God has a reason for everything. A story in which Superman confronts religion can open up a bit of a can of worms, not necessarily in a political sense, but because of who he is.
Throughout the issue, Superman is referred to by the elderly woman as an angel. On the cover of the issue, he is depicted descending on a crowd of suffering people having large red wings, rather than a cape. This initially bothered me because I wondered if it would be used to claim the hero as an avatar of Christianity somewhere in the issue. This does not seem to be the case, although it would not be the first time that Superman was given a messianic motif. The Christ-figure symbolism even played a role in his latest film, which is misleading considering that his creators were Jewish and many writers have thought of Superman as being a Jew (unofficially).
Although Old Testament metaphor is used to a great degree in Superman’s origin, tying him to one religion, an earthbound religion no less, is a mistake, just as it would be to tie him to one nation or ethnicity. Superman is an alien being whom has adopted Earth as his home, and all of its inhabitants as his neighbors. For Superman to be portrayed as being of any human religion lacks the fundamental truth of his character: he is not human.
The religions that humanity has conceived for itself are myths and symbols that are exclusive to what we have known as a species, and what we still struggle to find answers for. Everything from our human life span to the yellow sun that Superman’s physiology reacts to plays a role in these religions. They are our religions. Superman might look like modern male Homo sapiens (strange how both his species and ours are at common evolutionary points), but he is as close to our species as a dolphin is to a Klingon. He is a different creature altogether, and therefore it is doubtful that he would be able to relate to our religions. They would probably just serve as another example of how, in spite of his efforts, he will always remain an outsider.
Philosophically, I would expect Superman to at least feel very strongly about protecting the Earth after the destruction of his home world. Sadly, many religions that made a priority of being mindful of the Earth and the web of life that all of its beings exist in are not as popular these days. It would seem to only make sense though that Superman would convey some kind of environmentalist message, but for some reason this dimension of his character has been overlooked.
Another aspect of his character that would affect him philosophically and spiritually is his scientific mind. Like his father Jor-El, whom he greatly admires, Superman possesses a keen mind for science, as reflected in his domain, the Fortress of Solitude. It would be hard to imagine someone like him believing in something without thoroughly questioning it as a scientist would. And considering the things he has seen and the places he has been, it would be hard to imagine Superman limited to religions that base creation here on Earth.
One of the great things about a character such as Superman is how we can use him to see ourselves through the eyes of an outsider. Not to just reinforce what we already know about ourselves, but to question those things. It is not wrong to have Superman confront religion in a story, especially since the character and his creators have very strong ties to an earthbound religion, Judaism. But let us not forget all the potential that such a character has as an influential factor on our species from a vantage point that we will never have.