What an intriguing question! Both Willy Loman in Miller's Death of a Salesman and Macbeth in Shakespeare's play are victims of their illusions of manhood and what it means to be a success. Willy Loman believes that a true man is one who is recognized and profitable in the business world, like Dave Singleton, or one who seizes opportunity, as his brother Ben did. He patterns himself after these idols, thinking that obtaining these dreams will bring him happiness. Of course, he is wrong. We know that Dave Singleton dies alone in his velvet slippers, and Ben is a ruthless man, deserting his mother and Willy to go off and seek his fortune, much as he father did before him. Willy does not accept his own reality--that he is an ordinary man, married to a woman who loves him very much, and that he never has been or will be a success, as he defines it. He has illusions as to what a true man is, which is why he looks at Charlie with disdain, cheats on his wife, and raises his sons to lie and steal. Willy does not consider character or integrity in his false ideas of manhood and success.
Macbeth is also deluded in his ideas of manhood and success. Lady Macbeth coaxes him to be a man and kill Duncan when he has the opportunity. This act, Macbeth and Lady Macbeth believe, will bring them happiness. Macbeth is convinced that becoming the king of Scotland is his destiny. Nevertheless, this action backfires. Instead of bringing him happiness, Macbeth lives in fear of his former friends, his conscience troubles him, and his relationship with his wife falls apart. His attempt to be the man that Lady Macbeth urged him to be causes a deterioriation in his character and a loss of everything that he should have considered important:
My way of life
Is fall'n into the sear, the yellow leaf,
And that which should accompany old age
As honor, love, obedience, troops of friends
I must not look to have.
Macbeth, however, realizes the error of his ways, and comes to understand the reality of his situation. Willy Loman stays lost in his delusions.