personal favourite order
gta vc stories>gta sa>gta4>gta vc<gta lb stories>gta 3>gta london<gta 2<gta 1
gta vice city stories because it has the most you can do.
large and alot of things you can do in san andreas and very replayable
gta 4 next gen graphics but alot of fun thing like businesses and gang warefare removed because of 360 disk size
gta vice city because it was the first to let you do alot of stuff
then the rest basically because they are sequel to each other
im sure the exspansions for gta4 would give it alot of stuff and probably put it at the top of my list though