Yeah, Vice City. But asking things like "Best Systems" or "Best Halo" or "Best GTA" are just dull, and they practically say "Post GTA IV in this topic." Because whenever the new game comes out, kid's instantly agree it's the best. They're all "OMFG! Carcrash blood fly-thru windows gettin DRuNK!! so much BETTER!!11one." They have to think, when GTA IV came out, was it as exciting as when Vice City or San Anndreas came out? The answer is definitely no. You probably wont admit it, and maybe you forgot, but it's true. And the first time you played Vice City it was almost gauranteed more exciting and fun then the first time you've played GTA IV.
It dragged the components from the other GTA's and just revamped the entire series. It's a shame it lasted only one game. But the real reason I loved San Andreas was simply the story. It was so immersing! (And I know people whine and moan about the gangster talk, but they make it seem like it lasts throughout the entire game -_-).
The character development and the flow of the stroy was absolutely impressive and shot the other GTAs away. In GTA III, your boring story of a (not very cold) killer who works his way through a bunch of guys just to kill one person. GTA Vice City, more tough guy nonsense. But with San Andreas, CJ was definitely good... there's an emotional side to his character and that's what I liked.
I ove the 4th one, but they took things out that where in GTA San Andreas that made that games awesome. like planes, and the gym, where u can get buff. So I'm going to have to go with San Andreas!