Quite possibly the greatest GTA game ever.
Storywise, this game is basically set out like all the previous games, you kill gangs, you're backstabbed, blah, blah, blah. Oddly enough, as much as Niko is of the most dangerous protagonist of any GTA game yet; he is also the most.....polite... That's right, polite as in; "Could you take me to Wooden Avenue?" and "If you don't mind, I would like to listen to a different station.". But don't let his politeness fool you, Niko can be very deadly if you push his wrong buttons.
As far as gameplay goes I'd say, what you see is pretty much an evolutionized version of the standard GTA formula. The gun system as well as the driving mechanics have taken a giant leap when it comes to gameplay. Blood splatters gruesomely everywhere with every shot, and you can actually bust through the windshield if you drive in topspeed and crash straight ahead (that's why we should wear seatbelts).
Graphically GTA 4 is absolutely beautiful, the character models can blink and move their mouths freely including pedestrians, the shading and lighting have given this a look very similar to the artwork shown in loading screens. All in all, I give this game a solid 10 out of 10. You seriuosly cannot ask for a better GTA game! I'm reviewing this late since I got GTA4 late.