What really irritates me in some of today's games are the ones that are supposedly "hard" but for all the wrong reasons (poor design,terrible controls etc.)
I always say "give me challenging games" but i want them to be cleverly difficult not "cheaply" difficult.If the controls,battle-system or any other kind of gameplay is perfect and functional 100% then yes,by all means do try and make them as challenging as they can be.
For example,a game that doesn't reward you of having the option to save it after you have overcomed a hard part is not challenging,its poorly designed and cheap.If the Designers want to make them challenging but in a fair way,they have to think harder than that.