I like SA's soundtrack the most. It's full of songs I grew up, especially since most of them are black people songs. Still, I prefer III and VC's soundtrack because SA's soundtrack has too much dead time. In III and VC there is always a song on any fucking station that I could play the game to, in SA, not so much. Still, it has the best *soundtrack*, but not the best one suited for GTA. Also, the commercials and talk radio sucked in SA.
The gameplay wasn't the best. It wasn't nearly as non linear as GTAVC's mission structure, the missions did not have multiple routes you could take to complete them, many of the missions consisted of by the numbers GTA missions, the difficulty was eased up considerably.
The story sucked. It had potential to be a good knock off of Boyz in the Hood and other classics, and be a good social outlook on the state of modern black America, but then it turns into fucking James Bond and stealing Jetpacks and bombing Jets and it makes no sense. GTA is about being a criminal, not be James Bond.
On top of that, SA has the least memorable cast in the console 3d GTA's - OG Loc is classic, Toreno (although he doesn't fit in the game at all), Tenpenny and Polowski, so is the stoner guy, but honestly those are the only great characters. The people you work for aren't interesting either. Since the second thing I like about GTA games, past the i can do anything I want gameplay, are the characters, SA disappointed on that front.
Further still, CJ is the worst GTA main character. In game he says shit like FUCK YOU and SORRY PAL, BUT YOU JUST GOT JACKED

but in the story he's a fucking moralistic pussy and it makes no sense. "YOU MEAN...I HAVE TO KILL HIM?!!?" You must be shitting me Cj. You have killed thousands you idiot. I think they did that because he's black and having a black main character who doesn't give a fuck would cast R* in a bad light.
The best thing about SA is the huge open world, and even then, there's tons of huge empty spaces that don't serve any purpose at all. In GTA1, 2, London, 3, and VC every thing in the cities serve a purpose. Not so much in SA.
Killing a fucker with a dildo is just lame btw.