Why didn't Willy choose to emulate Charley or Ben or even his father in Death of a Salesman?Is Biff's pronouncement about his father at the funeral...

Yes.

Biff's statement that
Willy had the wrong dreams is true. Willy's idea that he could become rich quick by
being well-liked and by being a salesman comes straight from a story that he hears about
a successful and well-liked salesman named Dave Singleman. The story he relates about
Singleman is that, out of a hotel room, this man would sell just about anything, and
basically that he has a sort of Midas touch to succeed in sales. When Singleman dies,
his success is so well-known that he had a funeral to which a lot of other salesman
attend. This puts Singleman, in Willy's view, in a very high level of
admiration.

Willy's father was successful but he abandons
Willy and Bernard when Willy is still a small child. Bernard is also successful and got
rich but he did invest a lot of time and effort in going into his business. Bernard's
success was a combination of personal effort and good luck. Charly and Bernard would
never come to the level of success that Willy aims to reach. The rest of the people, to
Willy, are just simply not good enough.

If Willy had a more
realistic approach at life he would have realized that nothing should be taken at face
value. He does not know exactly what sort of sacrifices Dave Singleman had to ensure to
succeed. He does not know anything else about the man, but the stories that are said
about him. Therefore, to follow the dream of another man's success is an action that is
meant to fail from the get-go. This is what Biff concludes once he sees how his father's
quest for the American Dream was futile, to say the least.