Credulity is stretched to the limit here. Tom Hanks is a good-man’s gangster; his son decent and loyal to a fault. Paul Newman as an Irish mob boss gets his crack at doing Al Pacino, and does so with verve. Jude Law rides out his bad-guy character in style. Sam Mendes’ follow-up to “American Beauty” is handsome 1930s gangland road movie about a father and son (Tyler Hoechlin does a fine job as son) that’s wry in its humor and carries an insurance policy against happy endings. Whether the whole equals the sum of a few lovely stretches — Newman steals the show — is debatable.