If you are anything like me, your dad loves the gangster/mafia film genre and has been watching them all your life. Here are a few that you must watch if you like films like this or are interested in getting into them.
The Godfather Part 1 (1972) and Part 2 (1974)
http://entertainment.time.com/2012/03/15/the-anniversary-you-cant-refuse-40-things-you-didnt-know-about-the-godfather/
This is a no brainer. If you like gangster/mafia films you have probably seen this trilogy. The third one isn't as good as the first two, and the sequel is close to being better than the first. My dad would argue that everyone in the world should see this at least once, and I would have to agree. Starring Marlin Brando, "The Godfather" is centered around an Italian-American family involved in the mafia. When the Godfather's son Michael joins the family business (reluctantly,) his entire life changes. Part 2 involves a story about the differences between Vito Corleone's life and his son Michael's.
Goodfellas (1990)
GiphyMy personal favorite, "Goodfellas" is a story about Henry Hill and his growth being apart of the mob scene. He has everything that he wants but doesn't acknowledge the problems it causes.
The Public Enemy (1931)
https://wifflegif.com/gifs/478942-the-public-enemy-old-hollywood-gif
This is an older film about Tom Powers and his sidekick Matt Doyle, who rose from poverty stricken lives to crime involved thieves, with enough money to support their families — especially Tom's mother.
Bonnie and Clyde (1967)
GiphyA crime loving duo, starring Faye Dunaway and Warren Beatty, Bonnie and Clyde meet when Clyde tries to steal Bonnie's mother's car. From there, they're hooked on each other and committing crimes with one another.
Pulp Fiction (1994)
http://www.cnn.com/2014/09/23/showbiz/movies/pulp-fiction-20th-anniversary/index.html
Starring Samuel L. Jackson and John Travolta, Vincent and Jules are "Hitmen with a penchant for philosophical discussions." This film tells the stories of not only them, but their boss Marsellus, and his wife Mia, a boxer named Butch, and a pair of robbers, Pumpkin and Honey Bunny.