It's hard to say cause it depends highly on risk vs reward the game offers. If the risk is too much compared to reward, the game became not fun and too hard but OTOH if the risk is too few compared to reward, the game became boring and not fun. I didn't say exactly what risk and reward would be cause each genre has its own risk n reward.
For action games, the reward is feedback and physical reward from successfully "connecting" the action and the risk is the obstacle and hurdles obstructing player from performing the action.