The difference with games such as Manhunt and films such as Hostel is choice.You can choose whether to simply slay your enemy quickly or take your time using whatever implement springs to mind.It encourages people to make decisions based on cruelty limited only by their imagination and the game rules in place(more so than the usual violent acts in games).
You don't have the power to make that choice in films.Imagine if you could though..actors/actresses doing your bidding.With graphics becoming more realistic the line between movies and games is becoming increasingly blurred.
Having said that,games or films(no matter how violent) aren't to blame.People with the constitution for murder will be tipped over the edge by any manner of stimulii..conversations,stories,pornography,games,films etc.Censorship in this manner is awful..it will not stop sick people killing and it will certainly guarantee this game's success with the very demographic the censors are trying to protect.