@awesam: You're right in that my use of weakness might have been an overstep, but so is your saying that he's resistant to magic. I should have said in my first post that Superman is vulnerable to magic (as opposed to saying he has a weakness to it). He has about as much resistance to magic as a baseline human does. Avada Kedavra would kill him.
@awesam: Sorry Sam, but in this case, you're wrong. Superman is definitely not resistant to magic. He's vulnerable to it. Googling either "Is Superman weak against magic?" or "Is Superman resistant to magic?" should provide sufficient proof.