depends on the nationality with this one =/ like slime date and all japanes fantasy have japanesse as the Kings or leaders, also maybe it has something to do that most fantasy are basically base in Europe... don't know just a guess
maybe if people read more native American myths as inspiration instead of Tolkien, prosse eda and beowolf we would see more diversity but eh what can you do?
basically beserk my friend which is pretty hard in realism and rape X0
there was one fantasy series that had a matriarchy recently... people called it mysogonist and racist cause the main character was blamed for a rape he didn't commit :>, funny how the matriarchal kingdome is mysogonist
Edit: Just Remembered Tolkien actually had a country full of Black peoples (kings citizense the works) south of Gondor called Harad, so yeah Tolkien has blacks they are just not the focus of the three books but the cut parts of said books (you can't writte about a world as expansive as LOTR in just 3-4 books :0)
http://tolkiengateway.net/wiki/Harad#References