GTA IV features 19 in game radio stations with 200 songs; ranging from Rock to Classic. Stations like The Beat 102.7 was actually mixed by the likes of: DJ Green Lantern, Funkmaster Flex and Statik Selektah. The station features artists and producers like: Nas, Swizz Beatz, Ghostface Killah, T.I., Freeway, and the list goes on.
I could go into detail with this but I'm @ work right now, but to answer your question: I feel that Rockstar is the best company for soundtracks when it comes to games. There attention to detail goes all the way past gaming. Enjoy!
Oh yeah check out GTA IV "Lost and Damned soundtrack; it contains an additional 54 tracks.