Many people wish to make Willy Loman a tragic hero. Unfortunately, he does not meet the criteria.
A king is a man of elevated status. Because of his status he is responsible for not just his own well being but the well being of the people the rules. As a result, the fall of a king affects the whole society.
Is Will Loman a man of elevated status? No, he is from the middle class and just trying to live the American dream. Is his life tragic? Perhaps tragic is too strong a word. I would say it is sad and at times pathetic but not tragic. His death affects only his family.
A king was believed to be appointed by god who must have believed that he was the best man for the job. Not even Willy's boss thinks Willy is the best man for the job.
According to Arthur Miller himself, his model as a playwright was Ibsen. His objective, like Ibsen's, was to explore real problems experienced by real people. Willy Loman is like Everyman rather then Oedipus.