Iago's Character in Othello

Shakespeare might very well have made the decision to name his play "Iago" and not "Othello," but I suppose he had a knack for catchy titles. Since it is Othello's tragedy, even if it is Iago's play, "Iago" would be an inappropriate title, especially since it is not Iago's life that is ruined, and although he takes part in most—if not all—of the action in the play, it still revolves around Othello. That notion aside, one might take the time to raise more important or deeper points of discussion surrounding and filling the play.
Notice that Iago's reason for driving Othello to ruin is jealousy. Iago was passed up for a promotion, and became jealous. So what did he do? He made Othello so crazy that he passed out in epileptic seizures, and so jealous that he killed his one true love, Desdemona. The most basic "eye for an eye," it is quite probable that this is Shakespeare's way of commenting on human nature. Every character that speaks of Iago calls him honest. Perhaps he was at one point, but it is obvious that he has always been a rascal. During the storm, when Desdemona, Iago, and the others are waiting for Othello to arrive, Iago jokes about women being fair and wise or fair and foolish, etc., and the others are entertained by his crassness. It is certain that they are all familiar with and fond of each other, and in their closeness, regard Iago as a sharp-witted, and even sharper tongued, shameless rascal. This combined with the fact that they all consider him honest, they hold him dear and, to their detriment, trust him.
It is important to note Iago's relationships with the other characters, and to see exactly how it is that he plays them like pawns. He pretends to be the one true friend, feigning concern and jumping at every opportunity to manipulate. He uses the trust of Othello to drive him crazy, and the trust of Cassio to lead him into a trap, for if he had not done as Iago advised, then Othello never would have had reason for his initial suspicion. His wife Emilia and good friend Roderigo are simply his ignorant accomplices that, even though some suspicion may arise in their minds of his motives, still do as he says and believe his lies.
But no such suspicion could have foretold what Iago had planned in his head. In every action, there came a consequence, and every consequence became an action in itself, spurring more and more action, until not even Iago knew what would come of it all.
Even the fool seemed unhappy in this play. What little we see of him is sarcastic, like a good fool, but at the same time it seems he is angry on his master's behalf—and rightly so. But I think that Shakespeare intended for Iago to be half fool, half villain, partly because of the entertainment he gave to the others in his roguish wit, and partly because he seems to win over his audience for a while. You don't know what to feel, because at the same time that you pity the Moor and his young bride, a hidden part of you might take excitement in Iago's deadly mischief. I believe Shakespeare knew that, and that is why he delved so much into Iago's mind, with all the long speeches and asides. One cannot hate Iago, as much as one might try, because part of him resides in all of us.
Perhaps that is the message that Shakespeare was trying to convey. Everyone can be vindictive and revengeful at times, and incredibly flawed. The flaw that created the play was Iago's, in that he sought revenge on the wrong person. It wasn't Othello's decision to have Iago passed up for a promotion, but he, like most would do, misdirected his hatred and in doing so ruined several lives.