Jor-El as God
The Christian overtones begin early in the movie with the opening lines, spoken by Jor-El to Superman in which he says,
"You will travel far, my little Kal-El, but we will never leave you-even in the face of our deaths. You will make my strength your own. You will see my life through your eyes, as your life will be seen through mine. The son becomes the father. And the father, the son."
This shows Jor-El, father of Superman, to represent a God-like figure, giving his powers to his only son, as God did to Jesus, and the part of the son becoming the father and the father becoming the son is a staple to the Christians beliefs that God is three entities, the father, the son, and the Holy Spirit.
Jor-El furthers this comparison with another quote by saying,
"Live as one of them, Kal-El, to discover where your strength and your power are needed. Always hold in your heart the pride of your special heritage. They can be a great people, Kal-El, they wish to be. They only lack the light to show the way. For this reason above all, their capacity for good, I have sent them you... my only son."
This is strikingly similar to the reason God sent Jesus to Earth, to be the light that guides humanity, and to save them from their sins. Superman also fulfills this role as a beacon of ‘good’ and helps to protect and save, though more from the sins of others then from themselves, humankind. Not to mention the special heritage, a theme common to Christ and his divine birth. Both came from another place, Krypton and Heaven, in order to guide mankind along the right path and both were sent by their fathers.
Superman's alter ego is mild-mannered Clark Kent, reporter at the Daily Planet. He switches between these roles to live on Earth as both man and superhero. Jesus also had a dual persona, that of a man and that of God and the Holy Spirit. These dual personalities, as both man and something higher, is another comparison between Superman and Christ.
All Knowing Superman
Another similarity to Superman as a Christ figure is when he floats high into the stratosphere and listens to the world with his super hearing. From here he can hear the calls of help and cries of people in need of his assisstance. This is much the same way as God can hear our prayers in Heaven. Also, much like how God knows all, Superman can hear everything that is going on in the world. He reveals this, and the fact that the world needs a savior and that he is it, to Lois by saying, "I hear everything. You wrote that the world doesn't need a saviour, but every day I hear people crying for one," which furthers the comparison between Superman as being a Christ-like figure.
Lex as the Devil
Another comparison between the story of Superman and the Story of Christ is the inclusion of a Devil-like character, Lex Luthor. Lex is an evil genious that despises Superman, much like the Devil despised God. Lex shows this comparison by stating, "Gods are selfish beings who fly around in little red capes and don't share their power with mankind," in response to Kitty stating that Lex wanted to play God. Lex wants to create a new world where he is the leader, despite how many lives will be payed for it, much like the Devil wanted to usurp Heaven and have the power of God for himself. This inclusion of a Devil-like character further reinforces the religious, and Christian, overtones of the Superman story.
The Kryptonite Spear
Christ was flogged and beat by the Romans before being sent for crucifixion and while he was on the cross, he was stabbed in the side with a spear. Like Jesus, Superman was beat as well, not by the Romans but by Luthor and his thugs. After the humiliation and beating, Luthor stabbed Superman in the side with a shard of Kryptonite that resembled the head of a spear as shown in the pictures. This is another reason why Superman is portrayed as a Christ figure.
Death and Resurrection
The final comparison between Christ and Superman is how both of them died to save the world and came back from the dead. Christ died on the cross to abolish sin from humans, saving us in the afterlife while Superman 'died' lauching a collosal hunk of Kryptonite infused land into deep space to save the lives of millions of people, and the world from Lex's evil plans (also interesting to note that he falls back to earth with his arms outstreched as if he were on the cross). Christ is buried in a tomb and is discovered missing three days later as he had resurrected from the dead to speak with his disciples. Superman flat lines in a hospital and goes into a coma while the world waits eagerly to hear whether he lives or dies, until one day a nurse enters the room and he has dissapeared. Superman is last seen telling Lois that he will always be around, much like Jesus had told his disciples before.