Aristotle also said that a good tragic hero is a hero who is "better than we", either due to superior smarts or social status, and someone who possess a tragic flaw.

Oedipus is greater than we are in a few ways, according to Aristotle. First, one thing he meant is "greater" in terms of social standing. He believed tragedies should be about kings and nobles, in other words, not commoners. But he also means a hero - one who shows superior qualities, and Oedipus certainly shows that in his commitment to pursue the truth. Even as the revelation that he is the killer becomes more and more apparent, he never ceases in his pursuit of it, never tries to use his royal standing to divert the investigation. He is firmly committed to the truth, and suffers for his strength in this matter, which makes it tragic. As to tragic flaw ... you'll often be taught that Oedipus's flaw is his anger, which made his kill Laius, but I think this undercuts the tragedy in this play. Oedipus is an innocent in the true depth of the crime - he didn't kill his father, he killed some guy on the road. The fact that it was his dad? That's the fate's doings. But the lack of a "tragic flaw" in the sense that Hamlet has one only makes the tragedy deeper, and him a greater tragic hero.