One of the best games I have ever played.
The single player game alone would have done it for me. The storyline is so much more immersive than in any other GTA. The graphics are actually good, which is a first for a GTA. Rockstar fixed a bunch of problems and it really effects the game, more than I imagined. For instance, they added a cover system, which turns any gunfight into a strategic and exiting showdown. They added a GPS which gives you turn-by-turn directions to any destination. This can be very usefull, keeping you from checking the map every 10 seconds on the pause menu. The map also shows you how far you must run and where the cops are when you have a wanted level. Drive-bys are now fully aimable and you can switch between a handgun, submachine gun, and grenades that you drop out of your window as you drive. The phone makes recieving missions a lot easier than before. The radio is great as always, and there is many, many more things that I failed to mention that will blow you away.
The online multiplayer is a nice distraction to the main game, enabling you to go online with 15 other people. It's no Halo or CoD4, but its a good online multiplayer that has never been seen in this series.
All in all, this is a must have for any PS3/Xbox360 owner.