Obviously GTA V.
GTA V has lot of realistic thing GTA SA Doesnt have
-Better Cover System
-Better Wanted Level System (in GTA SA You must go to stupid pay n spray or collect bribe bullsh*t)
-Franklin > ''slave" CJ
-Better Steam Version
And more of endless stuff
GTA V is the GAME OF THE CENTURY and the only game that can beat GTA V is GTA VI