I think you raise a very good point, Steel. I agree many games, or any media for that matter, use modified versions of English to portray the way characters may speak, by introducing foreign sentence structure or vocab. My pickle with GTA:SA really doesn't have anything to do race, and I think it was a mistake on my part to refer to the issue as 'black lingo'.
In a nutshell I guess I found it frustrating because it did more than replace a few words. Its been a few years since I played it, but I remember there being metaphors I found bizarre put back to back and then there may have been some altered vocab on top of that. I think a good comparison to this would be A Clockwork Orange (the book), where quite a large amount of the vocab was replaced and then used in metaphors, leaving me feeling alienated from the story. I felt the same thing with GTA:SA and thats why I didn't get very far in it. I shouldn't have brought the issue of race into my classification as that really didn't have much to do with my quarrel with the game.
Again, it has been a few years since I tried to play it, the issue I'm describing may not be as prominent as I remember, but thats what went through my mind as I tried to play it.