If I look at the cooks around me, including my hubbie who is a master chef extraordinaire (In my books)
I would say that a good cook is:
passionate about all things foodie,
loves being in the kitchen,
has fun with food,
is experimental and a risk taker yet knowledgable in most aspects of cooking,
has a desire to please the palate,
worries about what the food looks like on the plate as much as what it tastes like,
and desires to know more, try more, and grow daily.
Obviously, there are techniques and skills one can learn and master but ultimately a good cook, for me, is someone with a love and heart for food!