Creon is portrayed as a pretty stand-up guy. He shows himself to be honest, forthright, and even tempered. The best example of Creon's reasonable nature happens when Oedipus accuses him of conspiracy. Instead of getting all mad and talking junk to his paranoid brother-in-law (and nephew), Creon offers a rational explanation as to why he has no desire for Oedipus's crown.
For one, Creon already has all the power he wants. Because he is the brother of Oedipus's wife, he basically has the same amount of status as Oedipus. Everybody sucks up to him to try and get to the king. If Creon had the crown he would have basically the same amount of power but ten times the headache. Who would want that? In this scene, Creon’s rationality stands out in stark contrast to Oedipus's angry paranoia.
Creon's argument is also strengthened by the fact that he's the one who gave Oedipus the crown in the first place. After the death of Laius, Creon was the King of Thebes. When the Sphinx started tormenting his city, he proclaimed that anybody who could solve her riddle could have his crown and the hand of his sister, Jocasta. Oedipus solved the riddle, and Creon proved to be a man of his word. A person who was truly power hungry would've gone back on his promise.
In the last scene of Oedipus the King, Creon also shows himself to be quite forgiving. Rather than mocking Oedipus, who has just accused him of some pretty terrible things, Creon is gentle. He brings the mutilated and grieving Oedipus inside, away from the public eye and also promises to care for the fallen king's children. In the end, it is only at Oedipus's request that Creon banishes him from Thebes.
Creon doesn't come out quite so well in Oedipus at Colonus and nowhere near as good in Antigone. To learn more, check out these next two plays in the trilogy.