James Brown = NFL
Bob Marley = EPL
Stateside, James has had a bigger impact overall and his music has touched various genres and artists. When MLK got shot and JB was in Boston, he put on that free show and was able to keep everything calm. Fairly certain Bob had a similar situation when there was a presidential election in Jamaica between two rival parties (Manley vs. ???). Not sure younger generations know about Bob and James from that perspective.
Bob is a bigger icon globally. He was a great musician in his own right but I think "who" he is and what he represented stretches further than his musical impact. Plus Bob died early so there's a 'Tupacification' of his legacy. I'd be curious to see how he would be viewed if he was still alive today...or at least lived as long as James.
JB is quintessentially black American...white people here aren't wearing JB t-shirts. They WILL sport a Bob Marley shirt and probably not even know a song beyond 3-Little Birds.