Manhunt is one of my all time favourite games, seriously, I stopped my very important in-very-soon coursework just comment.
While some people probably dismiss it as senseless violence, which, with no inspection at all it was, rather if you seriously thought about what you were being made to (or had to do depending on how you view it) do in order to survive there are many deeper questions you can ask yourself about morality and human nature. I've no idea if Rockstar planned it that way (they probably did) but it was an awesome game. And, I also agree that manhunt 2 was a complete failure, I played it for about three hours and realised that it had very little appeal. A manhunt HD or even non HD re-release would be very welcome, or even better a new game, based on the original perhaps a continuance.