Unlike the Greeks, we don't have a zillion different words for "love" that all have different connotations.
I love people in general. I feel a caring and nurturing feeling for strangers on the street. I like to cheer people up and do random acts of kindness that they aren't expecting (one guy nearly broke into tears when I bought him a newspaper....50 cents, not like I bought him a house).
I consider this to be a kind of love for my fellow human beings. I believe that all people deserve some level of love and compassion. I place my parents into that category of "people I don't know very well but still deserve some love and compassion".
This is different to me than, say, the deep love I feel for my husband or the heady love I felt for my first boyfriend or the kind of love that stems from knowing that person will always be there for you no matter what (ol' reliable).
Thus I can love my parents, without expecting anything in return from them.
Just my 2 coppers.