Unlike the previous Grand Theft Auto games, which boasted the talents of numerous well known actors such as Ray Liotta, Samuel L. Jackson, Timothy Spall, Garey Busey, and Bijou Phillips, Grand Theft Auto IV features a significantly reduced cast of celebrity voice actors. Among the list of guest appearances are Golden Globe Award winner, Ricky Gervais, and First Sunday actor, Katt Williams, who play themselves in Liberty City’s comedy club.Wikipedia: Grand Theft Auto Voice Actors

Shortly after Grand Theft Auto IV's release in May 2008, the main voice actor, Michael Hollick, spoke to The New York Times about his experience voicing the game's main character, Niko. In this interview, he spoke about the fact that none of the actors received any royalties on the game's sales. This is standard practice in video game idustry for voice actors, but it's different than any other form of media, and Hollick saw it as unfair. The article goes on to quote a Hollywood lawyer as saying the reason for this is that the voice actors don't sell the game, like an actor might sell a movie.The New York Times: A Video Game Star and His Less-Than-Stellar Pay