Meh, it's a good game, but definitely not worthy of all the 10's and 5-stars it was getting. All the money, all the actors, graphics, story, etc couldn't be bothered to keep me interested in continuing the game if only just for the sake of continuing the game. It's like those flash games you play and complete just because you're bored and feel you have to.
The problem is CoD4 and Burnout Paradise were just a DVD change away. I keep playing missions in B: P because I want to beat them, damn it. Losing a Burning Route by 1 second only pushes me to perform better the next time. Burnout: Paradise dodged a 10 in GameInformer (the only magazine I read about gaming because it's free with all the shit I trade into GameStop) because of nitpicky bullshit like having to drive back to re-do an event. OH NOES!
GTA4 gets a 10 even though it suffers from the same thing every 3D GTA has: keeping the player motivated to complete the game. "Oh, you just have to slog through the first missions to get to the good parts." Bullshit. If you want a 10, you have to earn it. CoD4 and even Crackdown grabbed my attention early on and kept it. Crackdown just suffered due to the realization that it's just "drive around > kill bad guy > level up a bit." But, then again, that's all they promised. And it does that job extremely well.
GTA4 is supposed to be some blockbuster action movie/game. What's the big deal with action movies? They grab you early on and keep you. GTA4 lost this idea somewhere in between the graphics and insanely annoying missions and character interactions. Burnout and CoD4, at times, has made me so frustrated I've tested the tensile strength of the plastic on my 360 controller (it lost once). GTA4? Meh, who cares. I'm just not into it enough to care. And that says loads about it's rating.