It could be the one and only greatest game I've ever played. It's got it all: gameplay, story, detail... wow.
Let me just say the game is so vast and immensely deep, I see something new the developers put into it every day. So what is typed below is nothing compared to what you actually see in this game, it's crazy.
Storyline: Very good. Nikko is probably my favorite video game character. The storyline and characters are very realistic. The voice acting for this game must've taken ages because every character has their own personality that is incredibly rich, it's stunning. He came to the U.S. to chase that American dream, among other things, to get away from his past and start anew on the right track. Problem is he gets caught up in trying to help his cousin and his friends out with bad guys and, well, the rest is up to you really (it's very open ended). Probably more so than other games that are renowned for that.
Gameplay: Fixed it up quite a bit since San Andreas. There are lots of new things that can be done in combat, in vehicles, etc, it's ridiculous. Fighting is a lot more interesting; they've added a more strategic aspect to fist fighting that sort of includes combos. They've added a "take cover" feature that works perfectly for insanely action packed gun fights. Everything runs very smooth and realistically. Cars have their own individual handling and attributes which only backs that up more, among other things.
Graphics: Very good. Sadly the game didn't come out for only one console, which usually allows for graphics to be even better than on multiple platforms, but they are actually very well done in this game. Sometimes it looks so real, I just drive around and trip out on the detail. Way better than it's predecessors.
Detail/Depth: Like I said, I find something new about this game everyday. The city feels alive, with all of it's rich characters, immense capabilities and things to do. The AI on the streets even have their own feuds and conversations which makes the entire feel of driving around the city surreal, absolutely surreal. I really can't even begin to explain all of the things you can do in this game... it's probably safer to just say you can do anything you want; from making an honest living as a taxi driver or vigilante, to embarking on one of the most entertaining campaigns/storylines I've ever seen.
Each of these sections should have their own sub categories of important things in the game related to them, everything is so widely developed.
Theres been some controversy as to the extent of the violence, language, and sex in this game, but it's really not more than any of the craziest movies that come out these days and all of that isn't even the point of the game. It's not like you start the game and someone comes up to you and says, "Hey, go kill a bunch of innocent people and cops and at the end of the day I'll give you a hooker and a line of coke." Yes, you can do most of those things as much as you want, but that isn't the point of the game, it only adds to the realism. And you'd be missing out on what may be the greatest video game (for many many many reasons) that I've ever played in my life.