Time and the tragic hero: non-classical tragedy
In classical drama, plays followed the three unities of place, time and action. Each unity had its own set of specific rules. Othello follows these unities more closely than many of Shakespeare's plays though the play does contain an interesting trick involving time. This "double time" as it has come to be called occurs when we consider how long Othello and Desdemona have been apart before he accuses her of adultery with Cassio. Seemingly, the two have had no chance to be together, since they did not travel to Cyprus on the same ship.
In accordance with the traditions of classical tragedy, most of Shakespeare's famous tragedies involve the fall of a great leader. Think of "King" Lear or "Prince" Hamlet. Othello is a different kind of tragic hero, a general, but not a major figure in the government of the state. In many ways the play is more a tragedy of domestic life rather than of affairs of state.
Perhaps the play owes as much to the English moral play as to classical precedent. If Othello is the central character, why does Iago have more lines? Does Othello play a role in his own downfall or is he just a victim of Iago's deceptions?