Jackson and Mac are Louis Hinds and Floyd Henderson respectively, two retired soul musicians who haven't spoken to each other in over twenty years. When Marcus Hooks (John Legend), the former lead singer of their group, dies, the two uncomfortably reunite to take part in a memorial concert for him, travelling cross-country together by car to do so.
Jackson and Mac pretty much make the film what it is, with performances which are solid if not exactly challenging for them in many respects - Jackson is essentially a toned down version of Ordell Robbie, his character from 1997's Jackie Brown, and Mac is for the most part his own stand-up persona. There is chemistry between the two, with Floyd and Louis' banter going back and forth pleasingly throughout the film. The soul music performances are also enjoyable, and an impromptu number by the pair stranded by the side of a desert highway with the car radio turned up is one of the film's highlights.
The music used throughout the film is also a strength, with the original compositions pleasingly faithful to the soul and Motown era and the other songs on the film's soundtrack selected with care.
Story-wise, the film is pretty simple, lacking depth in a number of areas. There are a couple of poor choices - an attempt to develop one character into a more credible villain, for example, falls flat on its face. Things feel like they run out of steam as we head into the final act, with some muddled plotting and actions that seem either out of character or just plain stupid.
The key issue is that of character depth and development, in that both are woefully lacking. Floyd and Louis are supposed to have ignored each other through hatred for over two decades, and yet the transition to them cooperating feels far too simplistic. Both characters don't really go anywhere from start to finish either; they're both pretty much the same at the end of the film as they were are the start, just in a different geographical location.
Characters in the supporting cast are about as deep as a paddling pool with a leak, receiving even less development than the two leads. When Cleo (Sharon Leal) joins the two men on their journey after they rescue her from a life of spousal abuse, her transition to backing singer is almost insulting in its ease. Others, such as Adam Herschman's Phillip, just feel one-note and lazy.
Despite these faults, the film is still enjoyable and entertaining, thanks mostly to the natural ability of Jackson and Mac. Ironically for a film entitled Soul Men, it's a fundamental lack of soul in the story and the characters that ultimately drag it down.