Nice?!

A friend talked about definition of a nice person in her blog several days ago. I actually never gave deep thought on it until then. I would normally consider myself a nice person. Why wouldn't I be? I care about my friends. I am friendly (well, most of the time anyway) and pleasant (when I am not tortured at work) But like my friend said, does that really make me a nice person? When I am nice to my friend, do I really not expecting anything in return? Or I am nice to them because I want them to like me? If that is the case, am I just being selfish? I used to think that I could I put more effort into a friendship and don't expect the other person to do the same. I understood you can't really tally who is giving more in a friendship and I am just doing what I want to do: to care for my friends. Not until later when I need my friend 's help and got rejected, then I know I was expecting something more. It was never a one way. Though I understand my friend is that kind of person, I can't forgive my friend for being so selfish and not helpful. If I am as nice as I think I am, I shouldn't expect my friend to help me in return. If I do expect something from my friends, then all this times am I really just keeping tab with my friends so they can return favor in future?