I like low-to-medium difficulty but medium-to-high intricacy = I don't like losing but I like (at least the illusion of) victory coming through sound strategy / deft control.

I never play any games on hard mode, nor stick with games that cause me any frustration.
But I also invariably walk away disappointed playing the likes of Fable 2 or the new Prince Of Persia, where victory is inevitable and the act of winning has been reduced to nothing more than tapping a button.

My ideal is Guild Wars, Bioware & Square Enix type difficulty ; tons going on in combat, though without micromanagement, and much importance placed on strategy /set-up - but underneath all the bustle you aren't really likely to lose unlose you blunder or shouldn't have picked the fight to begin with.