PixelBoy: I disagree, as having to replay the same part 50 times wasting 15 minutes each time is not my idea of a good time...
But, OTOH, I must say that I did indeed complete Hitman with no difficulties. In fact, for fun I even played a couple of more difficult missions, like the hotel and the jungle "kill 'em all" style, and managed to do that without any save options available. So in the case of Hitman, it at least can reasonably be done.
But imagine some sudden death games, like Sierra adventures, with no save options...
I didn't really mean games having no saving, just not save anytime. Of course most games require some sort of saving because they are too large to complete in one sitting. Even Hitmans sequels had limited saving due to the larger levels.
For me nothing kills immersion or tension more than an obtrusive save anywhere save system. And you cannot just ignore it and not save in a save anywhere game, because a games difficulty is built around its save system.
A more modern example of perfection in progression saving are the Souls games. The system punishes you for being lazy, careless and inept and rewards for being careful, diligent and playing well and employing risk assesment- the reward being the game feels easy. That's how saving and difficulty should work imho.