Of course I played GTA: SA and I really enjoyed it. But GTA IV is just much, much better than any part before. It was a real evolution in this serie. It has unusual atmosphere, great plot and, most important - it was highly immersive.
I thought that new GTA will be common to the previous one...
Unfortunately - it will not. GTA V is probably going to be just another Saints Row...
Now I'm waiting for Watch Dogs, which is probably going to be such an awesome game.