Great question. Othello is my favorite Shakespeare play for the following reasons:
- It has a clear tragic hero and villain. Whereas Macbeth has a hero turned villain (Macbeth), Othello pits Othello (hero) against Iago (villain) with Desdemona caught in the middle. The play is focused entirely on these three: there's no extraneous scenes, characters, or dialogue to interrupt Othello's tragic fall.
- It most closely resembles Greek tragedy. It most closely achieves Aristotle's three unities: of time, of place, and of action. The play has no subplot, and it has the smallest cast (13, I think) of all Shakespearean tragedies. After the shift from Venice to Cyprus--the action, place, and time are focused on tragedy. Hamlet and King Lear involve subplots, but Othello remains focused on our big three only (Othello, Iago, and Desdemona).
- Othello is realistic. It is a domestic tragedy. As such, it doesn't need the supernatural (Macbeth) or madness (King Lear and Hamlet) to hook its audience. Rather, it simply involves a husband, wife, and villain--just like the classic stories of Garden of Eden (Adam, Eve, serpent) and Beauty and the Beast (Beauty, Beast, Gaston).
- Othello's language is beautiful, natural, and subtle. Hamlet's language is a bit overdone (too many words, monologues, and soliloquies); King Lear's dialogue is a bit too sophisticated (focuses on politics and philosophy); Macbeth's language is a bit too nihilistic (focused on meaninglessness). But Othello's language is realistic and powerful without calling attention to itself.
- Most of all, Othello was ahead of its time. It features a black tragic hero. It features a bi-racial marriage. It features a bed on stage. It features a murder on stage in that bed. It features a villain who has more lines than the tragic hero. All of these conventions were daring, controversial, and very modern. It's a wonder the play ever saw the light of the stage.
Othello is Shakespeare's only domestic tragedy. It is a tragedy between a husband and a wife, neither of whom are kings and queens or nobility of any kind. Desdemona is a senator's daughter; Othello is a general in the Venetian military. Other plays that involve domestic scenes, such as Hamlet, Macbeth, King Lear, for instance, are complicated by the politics of the area. The power of royalty comes into play, and the actions of the characters affect the welfare of the country. This is not so with Othello.
Further, Othello is a play that involves a marriage between two people of different races. Desdemona is a true Venetian while Othello is a Moor. In this play, these differences are paramount as Othello's downfall lies partly in the fact that he feels as if Desdemona would naturally be attracted to someone of her own race, a man such as Cassio. Othello's racial difference causes him to doubt himself as a good husband for Desdemona, and it is this doubt that Iago exploits.