The Tragedy of Antigone is not called Creon because Antigone is more important than Creon, she is more controversial, and she is more admirable. Antigone played a bigger role than Creon in that she defied the law and started the whole play's chain of events, eventually leading to nearly everyone's death.
When the play starts, it starts with Antigone talking with her sister, Ismene. She talks about burying her brother, Polynices. Even though Ismene reminds her that this would be illegal, she goes ahead and buries Polynices anyways. Because of this, Antigone is a more important character than Creon because this action alone started the play's entire chain of events. Without this, Thebes would have gone on as usual, and Creon would have been king of Thebes.
Antigone is much more controversial than Creon is. After Ismene tells Antigone that she will not help her bury their brother and reminds her that doing so is against the law, Antigone tells Ismene to "Tell [that I am burying Polynices], tell it! You'll cross me worse, by far, if you keep silenceNot publish it to all." Antigone shows extreme courage in doing this, not only because she buries her brother, but also because she wants her sister to call out to everyone what she is doing. Antigone does this, to some extent, to defy Creon (who is the one who will not allow Polynices to be buried) but also to allow Polynices to have a good after-life.
Antigone causes the death of three people, whether directly or indirectly. First of all, she directly causes her own death because she hangs herself, rather than starving to death inside the sealed up tomb the Creon had her put into. Second, she directly causes the death of Haemon because he loved her and truly cared for her and her did not want to live without her. Lastly, Antigone indirectly causes Eurydice, Haemon's mother and Creon's wife, to kill herself when Eurydice learns that Haemon killed himself....