There does seem to be slow polarity occurring over the merits of GTA4.
I've always treated GTA games as something of a toy where I'm make up my own objectives that sometimes coincide with the game's story and other times have nothing to do with it. To date, I've never completed a GTA game; I found all their stories to be relatively uninteresting except for the opportunity to open up new areas or features in the game. In that respect, GTA4 is winning for me because I quite like Nico as a character, which is a first for me for the GTA series.
As far as the open world game goes, I appreciate the focus over the splurge of features from previous games. I don't miss the flamethrower or the tank or having soldiers chase me in a max-star chase; they just seem gimmicky in retrospect and not something I particularly found to be overly fun. Sure, maybe I'd try to survive a max-star hunt in a hard-to-reach corner of the map a couple of times but, after that, the appeal wore off. Why include a feature I won't want to use? Seems a waste.
Instead, the core of the game seems much better refined. The cars drive better, the gunfights are much improved, the cops are more interesting to try to escape from (no more suicide ramming unless they're getting really serious) and there's more, well, character to the world. I drive by the first apartment for nostalgia from time to time, just cruising... 'til some idiot crashes into my recently painted Sabre GT where I have to leap out and kill that mofo, blow up his car, shoot some cops and generally go totally postal.
I'm about half way through the game. I think I've played a bit less than the rest of you but, even so, I probably spend around half my GTA play time just driving round, trying to get that five rolls from one crash achievement (which is proving to be tricky) or just peering at the street signs. Hell, one evening I just watched the TV for half an hour.
It's a game I can play my way, whatever that way might be this evening. In that respect, it is incredible.