Typically, video game inspired rap is left to parody videos. There’s plenty to be found out there, so I won’t bother linking to any. They may be good from time to time, but they’re still typically done in jest. Its rare to find any music really that takes video games seriously, the protomen pops to mind.
Sammus, on the other hand seems to have put out an actually decent rap album based off of the game Metroid. At least it would appear so from what I’ve heard on soundcloud. Here’s an example.
I’m actually listening to this album right now and enjoying it considerably.