Grand Theft Auto: San Andreas is a great game and is very welcome over Vice City.
The reason I am giving sound such a low rating is because the radio is really, really bad. Most of the channels are rap, which is not quite appetizing for a large ratio of people, and one is country, which is actually worse than the rap. The rap isn't even the best of rap, on the contrary, they took some of the worst rap I've heard in a while and put it in the game. With the exception of about two radio channels, I usually just turn the radio off. But yes you can put your own mp3's in the game which makes it a bit better.
The graphics haven't improved a lot but they are definitely better than previous GTA's. In Vice City every third person was clone of another person. Now it's more like every 15th. The models are better than before as well. For some reason, the cars got less cool looking than in Vice City, even though we've gone up the timeline.
The story line is very well done in this and there are a lot of awesome characters like Cesar and "The Truth". It manages to tie in characters from the previous two games to the storyline although there is sort of a time lapse on two characters that were in Vice City and they are actually younger than they were in Vice City for some reason. I know a lot of people say that the storylines in GTA games are always the same but does it really matter? What else could they make it be? Settle for second best in the crime families? Petty Theft Auto?
This is where the series really shines. I can play this for hours and hours and not get tired of it. There is so much to do and see that you won't get tired of it either. You can just drive around the interesting parts of the map mowing down innocent/guilty bystanders or get a bunch of cops on you and see how long you can last, or search the map looking for intentional or non-intentional jumps.
It's a great game, just don't buy it for the minors if you don't think they can handle the tons of cursing and suggestible content, and don't go blaming Rockstar or games for "corrupting" your kids.