Hey this is NHouseman with my experience on GTA 4 (Grand Theft Auto 4).lets start with the single player mode.
The single player surpasses its grand theft auto predecessors, the graphics in it is awsome. you get to drive a lot more vehicles including a moped and a forklift. It has a good story line and you are able to change the outcome of the story by choices you make in certain points of the game.
Now how about the online multiplayer gameplay. which is un imaginable. It has a vast amount of different online play modes like a free play mode, cops and crooks, deathmatch, team deathmatch, mafia work, team mafia work, car jack city, team car jack city, and turf war to name a few of the vast list of stuff you can do online.
overall i think this is the best game of the year hands down. GO GTA 4 