The only one I had played before this year is IV, now having played 1, 2, 3, VC & SA too I must say Vice City, the shooting is a little off and San Andreas plays infinitely better, but the whole 80s Miami Vice thing taken to such an over the top extreme is far more entertaining than anything any of the others had to offer, 4's good too and I liked Niko but I don't know Vice City clicked better with me, you'd think I'd like San Andreas better since I do actually like Hip-Hop and plays better, but I find Carl to be a horrible person and I hate him, which is kinda dumb given that this is GTA, but I think Tommy was better because he was kinda cynical and was pretty much a self aware character, not necessarily of himself but of how ridiculous the world and characters of Vice City were and I found him to be an entertaining asshole rather than a hateable one.
Anyway I just found Vice City more entertaining.