I think this is tricky.
The core of my viewpoint is that it's all about whether a game is fun enough to sustain dealing with the difficulty.
That's kind of tricky, because a game that is too dumb easy, won't be fun anymore. But difficulty isn't a goal in and of itself.
If there were two similar games, one was way harder than it should be (say borderline impossible), and one was way easier than it should be, I'd rather play the one that is way easier. At least that way I might be able to have fun progressing/exploring.