Vice city is awesome, but San andreas friggin ROCKS.
If you like first person shooters, try Enemy Territory: Return to Castle Wolfenstein. You can play online against other players, its addicting as hell...I played it for about 2 years!
http://enemy-territory.4players.de:1041/
http://www.3dgamers.com/games/wolfensteinet/downloads/
btw, enemy territory is FREE
GTA has an unhealthy hold on me. I woke up this morning and decided not to go to church and to stay home and play GTA all day instead. Finally, I had to go to the store and realized I had to come home and take it out of the X-BOX and lay off of it for a while. Even though I'm in the middle of the boat missions and they're really cool.