People have different preferences, desires and needs. Based on those things, we choose whom we must love. Well, may be sometimes we do not really choose who to love; then it is called falling in love. Often, we grow in love. When we grow in love, we have made a choice of who to love. We should not confuse attraction with love. Often we get attracted to people, but if we were to choose, we choose based not on outward appearance but on personal characteristics, more like the heart being of a person.
A good lover is the one person whom I have this warm feeling towards. Their presence excites me and I cannot stop thinking about them. I think often that it would be great to spend the rest of my life in their company. I am not only attracted to them outwardly, I want to know more about them, I want to help them and I feel that their happiness and security are, to some extent, my responsibility. That makes for a good lover....that depends on who I am.
For others, a good lover would be someone who stands up to everybody, watches over them like a vulture and loves vulgarity. One loves the gentle types, another the aggressive, we cannot put them all in the same box. Each one his own.