e., as Aristotle puts it, is "either a higher or a lower type [emphasis added]" (Poetics, Part II, paragraph 1). Oedipus is in fact both: someone of great stature at the beginning but reduced to being a much-unwanted exile at the end. Othello shares that destiny of reversal of fortune, i.e., "a change from bad fortune to good, or from good fortune to bad" (Aristotle, Poetics, Part VII, paragraph III). For example, Othello starts out as the Venetian Senate's choice to lead the Venetian Army at Cyprus, but in the end he is stripped of his position of military leadership (Cassio replaces him in Cyprus) and is then deposed (or would have been) from Cyprus, had he not first killed himself. Iago, on the other hand, suffers no reversal of fortune from a high place to a low one. The only change for him is that he starts out jealous and despicable and ends up dead. That, however, is not the stuff of tragedy, Aristotlean or otherwise. Othello, as opposed to Iago, is also more tragic in the sense that he is both larger than life (he has a certain "magnificence" of personality and bearing, as well as a military status far superior to Iago's. And Othello is also, as a multi-faceted character of many moods; emotions; understandings (or not), and changes leading to a reversal of fortune, is far more imitative of a real-life imaginable person of similar...

Othello, not Iago, is both larger than life and lifelike in terms of his inherent dynamism, even if it affects him most negatively in the end. Othello also suffers a reversal of fortune as well, arguably similar to the way Oedipus does in Sophocles' Oedipus the King. Iago, though, suffers no such reversal of fortune or circumstances; he merely starts out as someone jealous; scheming; and malevolent, and maintains those same qualities throughout the play, right to the point of his being killed by Cassio.
Works Cited

Aristotle, Poetics [online]. The Internet Classics Archive. Retrieved December

11, 2006, from: http://etext.library.adelaide.edu.au/mirror/classics.mit.edu/Aristotle/poetics.1.1.html

Shakespeare, William. Othello the Moor of Venice [online]. The Complete

Works of William Shakespeare. Retrieved December 11, 2006, from: www-tech.mit.edu/Shakespeare/.html