I've been playing it for about a week, and I'm not too far into it (been fucking around more than anything, not really doing too many missions) but I have to say it is the best modern game I have played. The only games that would even be in its class are true classics like Zelda a link to the past, super metroid, Final Fantasy 2 and 3 etc.
The music is excellent. lots of stuff I grew up listening to.
the voice acting is incredible, and there are quite a few big name people.
the gameplay is ridiculous, the map is HUGE and theres an amazing amount of shit to do outside of the storyline, ranging from playing pool or basketball, to doing graffiti, to burglarizing people's houses and lots of other stuff. One of the most fun parts of the game is customizing your character. You can eat and gain weight, work out and get built, get tattoos, hairstyles and LOTS of different clothes. I wear different clothes for different activities.... like when I go do drivebys on my sportbike I like to wear no shirt and a german helmet with a spike and a green bandana covering my face (green is your gang, the Grove Street Families color.... the families is based on the Crips and the other gang, the ballaz is based on the bloods)... then I get changed into a jersey or a green hoody or something for other stuff.
it also has one of the coolest videogame characters EVER. Ryder. He's a crazy gangsta who is always smoking PCP, he talks LOTS of shit and he looks exactly like Eazy E. in one scene he is cooking up PCP and gives some to a corrupt cop played by Samuel L jackson who says "my wife loves this stuff"
gun material: this game makes me want to buy an open bolt KG-9