The thing I hate with GTA 4 is it doesn't know what it wants to be.
See Vice City and San Andreas weren't trying to be realistic, they knew the worlds were crazy. I remember pile-ups of "FBI" SUV's, killing each other trying to get to my character. It created a world in which simple fun was the most important thing, like say CoD online is. It's fun. However when I play games like Oblivion, Fallout, Mass Effect I get sucked into those worlds and this is where GTA 4 goes wrong for me. It's stuck in between those type of games.
Because of its technical superiority over its predecessors you don't encounter what I call "random crazy shit", like a car accidentally hitting another car and the passengers getting out and fighting to the death, no scripted things pure glitches in the mechanics. Maybe they're not even glitches, the programmers might have thought, that's fun why fix that?
GTA 4 takes itself a lot more seriously, it wants to absorb you into its world, the thing is it doesn't, well at least not in my case. Not like Oblivion, Mass Effect etc. do. So it's stuck there, not funny enough to handle like Vice City not serious enough to handle like Oblivion. This results in serious gameplay without the rewards for the effort you put into your character (and the game). It also results simply in a strange contrast between certain parts of the world. Like that crazy steroid guy (funny) and the Mafia boss, who I thinks supposed to be depicting a boss of the five families (serious).
It might just be me who feels this way but it made the game a bit pointless. I didn't play it for laughs, I wanted the typical gaming experience, to be sucked into a different world for a couple of hours. To be Niko, yet despite a decent storyline this fails. IMHO it betrayed what GTA stood for and we as gamers didn't get anything better in return. A decent game, by no means a great one.