Rockstar Entertainment has started working on a Rap sim type game. Considering they generally have hit the nail on the head with Hip Hop culture in the past, they may be the best chance at a decent rap sim.

There was one in recent years called Def Jam: Rapstar which i bought, it had potential but the mechanics was a little bit off and the creators made the stupid decision of using the censored versions of all songs.

As a dude who hangs out around rappers and has fooled around with it myself i also have to say one thing about freestyling. It is freakishly hard, even if you are familiar with how to structure structure and deliver lyrics. If you don't know that you are going to sound awful.

That being said i would love to see a game that does hip-hop justice. With careful song selection and finely tuned mechanics it would be possible.