I think some games don't necessarily have to tax you all the way to be fun...but that may just be me. Some enemies are meant to be whimps in the face of your power.
I agree. If I'm playing Prototype, for example, I expect to feel empowered because my character is a superhuman badass. However, if I'm playing a survival horror game like Dead Island, empowerment should be the last thing I feel. That's also why I think co-op hurts the game. Running around with three of your buddies not only ruins the atmosphere but the tension as well. Without that tension and atmosphere, the game becomes nothing more than an easy beat'em-up.