James Brown was an icon. So was Jackie Robinson. But they were legendary men in completely different ways – one a flamboyant soul visionary, whose influence still can be traced on the R&B, pop and hip-hop scenes, the other a stoic, yet aggressive trailblazer for race relations who broke the color line in sports nearly 20 years before the Civil Rights Act was signed.

So it’s all the more remarkable that the same actor was cast to portray them on film – Chadwick Boseman, who took on Robinson in 42 and now Brown in Get on Up, which though it could have taken more risks, is a fun, propulsive warts-and-all portrait of genius at work.

At its most successful, Get on Up portrays Brown as inhabiting a world of his own, whether he’s shielding himself from abuse and neglect as a child, reaching to make the rhythm in his head reality in his music or struggling against isolation and addiction later in life.

Boseman is the key, and given the accomplishment of his two recent performances, he may be the most successful actor you haven’t heard of, despite taking on such big roles. The actor himself it seems, has been overshadowed by the stature of the men he’s portrayed, an ironic measure of just how well he buried himself in the roles. Another journeyman actor, Nelsan Ellis, best known as the colorful Lafayette on HBO’s “True Blood,” establishes himself as the emotional center of “Get on Up,” in a patient and understated performance as the star’s long-suffering right-hand man, Bobby Byrd.

Director Tate Taylor, of “The Help,” is mostly successful in his endeavor, despite adhering too much to the tried, true and trite in the biopic – the wounded child motif appears throughout the film and he jumps willy-nilly in and out of the star’s timeline. There’s an emotional build-up in his choices, though, most notably in Boseman’s confrontation with Brown’s estranged mother, played by Oscar-nominee Viola Davis. Still, there’s a sense that while laying out such a unique artist’s story, Taylor could have embraced the license to be more daring in telling it.