Very close call, but San Andreas gets my vote. Simply for it's huge map, and the enormous variety of vehicles. I just love driving around the countryside or desert in a car and just enjoy the huge world, or take a flight in a airplane and view the cities from above, eventually parachuting down... and maybe wreak havok in a tank
I LOVED Vice City! I loved the look of it, the neon lights, the 80's feel of it. Tommy is my favorite protagonist, I think Ray Liotta brought so much life to the character. And the music was so great! Definitely the best!!
Easily San Andreas. That's the GTA game I've played the most. The game had many great elements and functions. Especially the great map with it's variation and the atmosphere in the game were super. I also enjoyed the missions and the soundtrack and there were many memorable cars and characters. This is also the only GTA game I played the multiplayer mode and it was super-fun!
Only two GTA games ever managed to blow me away, and those were GTA III and San Andreas. GTA III was so groundbreaking when it first came out, and it caught me way off guard - the first 3D GTA, what I always dreamed of. And then Vice City showed some real improvements over it, but despite that I still liked III just a little bit more. But it was San Andreas that managed to catch me off guard for the second time, and it hit me even harder than III did. Such an awesome map, so many features, and it still gives me hours of fun even today. So San Andreas is my favorite GTA.
SA, for me. I choose because of the map size and variety, and because of the large amount of vehicles (being the MT bike one of my favourite vehicles...). The game itself is really good, but IV just smashes it in most ways...