Sure, this is a rather silly movie, but we enjoyed it. The interplay among the three O'Hara brothers is spot on, and, not surprising, when James Cagney is on the screen, you really can't take your eyes off of him. Equally wonderful is the relationship between Cagney and Mary Gordon, who plays his mother. You can sense the affection within the family group, and Ms. Gordon, especially paints a picture of a woman who is the thread that binds the family unit together.
Though the plotline is so-so, this TCM article points out that director Lloyd Bacon, well aware of the script's limitations, encouraged the actors to ad-lib during the production. As a result, the dialogue has a bounce and energy to it. And while boxing match at the end does seem a bit prolonged, it gives the character of Pat time to recover from the circumstances that have alienated him from his youngest brother. O'Brien and Cagney do a wonderful job of creating a brotherly dynamic that it made us imagine Pat and Danny as children, with Danny always getting into scrapes from which big brother Pat needed to rescue him.
Normally, we love Allen Jenkins, but his Carbarn Hammerschlog is a bit over the top. One wonders how Danny could possibly see this rather insane man as a successful boxer (but that is Danny - always looking for the underdog!). It's one of the weaker aspects of the plot, but does serve as a means of getting Cagney into a boxing ring (the AFI Catalog states that Cagney did his own boxing in the picture).
We're also treated to a picture of bygone era in New York City - a time when you knew all your neighbors, and it was a fact of life that everyone knew what the other person was doing. One scene in particular - Ma O'Hara passing a bit of butter wrapped in a napkin to her neighbor via the clothes-line between their apartments, brought up memories of my childhood, when my mother would lend a bowl or some eggs to the neighbor through a narrow kitchen shaft window!
The strength of the film is that strong sense of family. Pat's anger at Danny's haphazard lifestyle centers more on his fear that Danny will not be able to help support the family when Pat marries and moves out than on any jealousy or dislike of his brother. And the relationship between Ma and Lucille also emphasizes the family as a unit - Ma is immediately welcoming to a potential new member of her family. Lucille senses that she is now an O'Hara, and seems to find in Ma the mother that she has lost (Lucille has a father, but it seems he may be widowed).
We'll end this discussion with a scene from the film, as Danny and Lucille get to know one another: