If we presume that the opinions of Ben are actually projects of Willy's own mind, then we can argue that Willy does achieve a realization that offers a rare, honest insight (for Willy) into his own character.
Willy has a final conversation with Ben before committing suicide. In this conversation, Ben argues against the idea saying that it is a"cowardly thing" to do.
Willy, to himself, never admits to being a coward. He insists that he can still achieve greatness or success some how. Yet, through his hallucination of Ben, we can see that Willy recognizes the nature of his character and the act of suicide.
He is not a success and never will be. In death, a cowardly death, Willy will claim some small degree of success, but no greatness. With luck, he will provide his family with $20,000, however, he will deprive them of his own presence and guarantee his own moral failure.