Southpaw is a boxing film, so it has to follow the tropes and metaphors of fight=redemption/validation, but it never really moves past that. Every boxing movie worth its salt—whether it be Rocky, Raging Bull, The Fighter, Million Dollar Baby, or Warrior—always has a new way to tell the same tale. In Rocky, we meet a mafia enforcer who boxes on the side, and guess what, he has a heart of gold. In Raging Bull we follow the life story of real life boxer Jake LaMotta. We follow him as he goes from a young rising star, until he eventually burns out due to drugs and abusive relationships, and then ends up doing stand up comedy. The Fighter gets up close and personal with drug addiction, Million Dollar Baby forces us to ask ourselves how we feel about euthanasia, and Warrior offers a twist on the boxing trope of the everyman risking it all for the cash reward, by having the last match of the tournament pitting the main character against his brother.
Now, seeing that boxing films have such a rich history of touching deeper issues while also giving us the "there is always hope" spiel, it's hard to fully enjoy Southpaw's 2-hour running time when it doesn't offer anything new, or even all that thought provoking. All of it's actors are good. Forrest Whitaker puts his own touches on the Mickey/Obi-Wan character. Rachel McAdams has a strong role as Gyllenhaal's wife, and the young actress who plays their daughter (Oona Laurence) is also quite good. That being said, that absolute best performance in this film is from Gyllenhaal, this is without question his movie. He embodies the character both physically (the guy is huge in this movie) and emotionally, making us believe that he is truly a guy who simply knows nothing else.
Now, having an actor give an outstanding performance certainly makes your movie stand out, but it needs more than that to live on in the memories of viewers. It's a decent movie, worth a one time watch, but after that, you'll likely find it hard to remember anything else other than Gyllenhaal's performance.