Bought GTA IV on release and I've only recently started playing GTA Racer online. Truly, as a stand alone game it would shine above any other.
Its hilarious and total anarchy throughout each race. You have all vehicles and weapons at your disposal and can race like a pro or use every dirty, underhanded trick in the book to win e.g. barracade the road and RPG everyone in sight! (not my tactic but it happens).
Not only this but the race takes place with the usual public and police living their day to day lives. Can't deny running a few over by er accident!!
Each race can be customised by the host, from weather, number of laps, weapons, tracks, police presence, vehicle type etc. The truth is if you start the race on a bike you'll probably finish in a highjacked station wagon. The funniest thing is the mayhem of the first corner when 10+ drivers collide and scramble for race position. After that its up to you what you want to do. Continue racing or get out of your car and blow things up! Standard racing game rules go out the window and the total gaming freedom is what makes GTA special.
Can't recommend GTA IV enough, especially for the knock down price.
The single player isn't as much fun as San Andreas but it still oozes quality and deserves to be part of anyones collection.