10... why 10 because this series simply deserves it.
Ghost in the shell is the anime which will make you a total psycho. The story is so deep so that the viewers need to analyze a lots and lots of things which is happening in the anime. If they fail at that then they may think this anime as a piece of junk. But if they somehow get in to this anime and were able to understand the whole story then I'm sure they will regard this anime as a total MASTERPIECE.
The things which the creator of this series have thought is simply outstanding. Things which he have mentioned in this series might actually be developed in the coming future.
P.S
Now even with the hollywood adaptation of this series shows how much interesting this series is...