It doesn't make any sense for hip hop (or any other music style) to be in a game only for the sake of being into a game.
However music styles (including not only hip hop but others as well) are sometimes related to other sort of styles (life style, art style, way of thinking, etc). This is something that can be put in a game and has been done at the past. The trick is of course that since we're talking about something that has to transfer some "feeling" (i'm not sure i can describe this but try to imagine :-p), it has to be made by people who know about it and love it.
See Tim Schafer's Brutal Legend. It is a game about heavy metal and the people involved obviously love this kind of music and style.
So for a game about hip hop, it needs people who are involved into and love hip hop

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