Dr. Faustus can indeed be considered a tragic hero, for a number of reasons. For one thing, he evokes pity and fear in the audience, leading to a purging of the emotions that the Greek philosopher Aristotle called catharsis.

Faustus is able to evoke pity since we can identify with him to a certain extent, seeing something of ourselves in him. Though he acts foolishly in making an unseemly deal with the Prince of Darkness, we can still recognize his mistakes as fundamentally human, the kind of mistakes that we ourselves could make under similar circumstances.

Faustus enters into his pact with the Devil because he wants to have more knowledge, and gaining knowledge is an intrinsic part of what it means to be human. Although we may not agree with how Faustus chooses to acquire such extra knowledge, we can at least sympathize with his desire to know more.

Both fear and pity are evoked in equal measure when the clock strikes midnight and it's time for Faustus to be dragged down to hell: fear, because Faustus' corrupted soul is set to burn in hell for all eternity; and pity, because it's not very pleasant to see someone consigned to the ultimate punishment for doing something that we ourselves might be desperate enough to do, depending on the circumstances.