Tragedy.

This play is technically a tragedy, but it has some aspects of a comedy in it. The comedies usually had people who appeared one way but were truly a different type of person. This is true of Iago. He pretends to care about all of those around him, but he really only cares for himself. He hopes to get Cassio's job by turning Othello against him while pretending to like Othello when he really hates him. He does the same with using Roderigo to get his money while pretending to help him get Desdemona.
The fact that this is a tragedy tells the audience a lot about what will happen. A tragedy means that all of the main characters will die in the end. This makes everything that the characters, such as Othello and Roderigo, say about death seem kind of comical, because the audience knows that they very well could be the ones to die in the end. I also believe that this adds suspense to the play, because the audience in anticipating that they will die. They are looking for what will cause the deaths. I think that this particular play is enhanced by the fact that the audience knows the outcome, because it adds suspense.