Defining the right difficulty might be on the hardest things to do in game development. Even harder than coding it, if you ask me.
Too easy is not fun, and too hard will only be enjoyable for player who deem themselves "elite" (I'd say the need a life).
However for my RPG games I always set three difficulty settings. Easy, casual and hard. Casual is for players who want to experience the game as hard as I want it to be. I like my games not too hard and not too easy. I play for fun, so a challenge is nice, but nearly impossible... yikes. Easy is for the "noob" (I hate that word), or rather players who have to learn how RPG games work, and the hard mode, well if it's a hard game you want a hard game you'll get. In my games you can only select this at the game's start as I did more than just making enemies stronger or weaker. For example the inventory space is bigger in the easy mode and smaller in the hard mode, and that's only the tip of the iceberg. Since there are people trying (and even succeeding) in completing Final Fantasy X without touching the spheregrid and without going crazy with Zanmato either, I guess it's wanted by some people. Well, now I can at least serve the newbies, the people who need a life, and the rest of us with one game. What more do we want peeps?