They are the earlier parts to the game but they are in no way lesser- just different, the graphics are only slightly better from 3 to vc to sa but the games are so good it doesn't matter. SA is the first GTA to add the role playing elements to the mix so it was a big difference from the earlier ones but I say DEFINETELY get VC and #3. In SA the more you practice driving each vehicle the better you get- the handling gets better, the more you swim under water the longer you can hold your breath and the more you shoot each gun the more your rating goes up- when you reach hitman level on the pistols or mini smg you can dual wield them - 2 guns are of course more fun than 1
Try shooting at an empty cars tires over and over your rating will go up that way too.