Maybe you should make Fun Space Game: The Actually Scary Fun 90s Shooter? Just a suggestion.
I prefer difficulties where you can alter them mid-game, but I do think you should be able to change back sometimes, because some games the shift from one to the next is enormous, as you mentioned in one of your older reviews (don't remember which one). I also think Max Payne didn't do too badly, as when you did better the enemies did become noticeably harder and better at killing you, then eventually they got too good at their job and scaled back again. It was a little blunt at times, but it worked as a system, along with the standard 'easy, medium, hard' malarky.
Maybe a little of both is the answer, don't overwhelm a new player, but equally don't let them fall into the trap of going too hard before they're ready for it.