Now that I have played the game for a bit, I have to say this...I have NEVER seen acting like this in a video game. R* totally nailed it in their choices.
Ned Luke is BRILLIANT as Michael. He really seems to get the nuances and is very conflicted as Michael needs to be. I see awards in his future. I can't get enough of his story and the way Ned tells it is tremendous. Can't wait to see him on Boardwalk Empire.
Steven Ogg is equal to the task as Trevor, although to me he is a bit of a one trick pony. But WHAT a trick! I believe he has created an iconic GTA character that will stand the test of time. I believe we will be seeing much of Steven in the future playing off the wall characters on TV and film. He is just a hoot to watch.
Shawn Fonteno seems to be the straight man of the three. He is terrific playing a gang banger looking to get out of the hood. He also has a lot of conflict in his character. Looking at his IMDB he doesn't appear to have anywhere near the experience of the other two actors, but is able to more than hold his own. I believe he is a natural. The dialogue flows naturally from his mouth, and he has a smooth rhythm that hints to a rapper type background.
Overall, again, I believe this is the most well acted game I have ever played. And make no mistake, these are NOT JUST voice actors. They are the real thing and prove it consistently with every mission and cutscene. That R* hasn't promoted their performances is a shame. Maybe they will after the game officially launches. I hope so. They truly deserve it.