We don’t know the details about the HD remake of God of War. If it’s just a case of attaining high resolution graphics, only, then that wouldn’t be that difficult,
but if we were to achieve the same graphical standard as in XIII with a PS1 title, then that would be a huge, huge task. Almost unrealistic. Even with a PS2 title it would be difficult. In the case of God of War, there weren’t really that many characters in the game — the main character and some monsters, maybe ten people or so. That would not be unachievable.