I am that diehard romantic that answers love to questions like these. "...faith, hope, and love...and the greatest of these is love..."
In my opinion love drives all the important decisions in our lives. We treat people the way we do because we love them, or dont.
We treat ourselves out of self love, or self loathing. It's all about love.
For me, it's duty. I need to do my duty in terms of what my family needs from me and in terms of what my work needs from me. I think that a major key to being a good person is doing what is needed of you, regardless of whether that is what you would most like to do.
I value empathy more than anything else. I think that people that have the capacity to understand how others feel will make better choices. This is why we teach children the Golden Rule: treat others how you want to be treated.
At the moment, I would say Personal Responsibility. I have the responsibility of making my life work, and being decent to friends and family, and any mistakes I make are mine. I cannot blame anyone but myself for troubles in my life, and no one else is required to fix those mistakes. Without knowing and accepting that I alone am responsible for my actions, deeds, and words, I am nothing but a pawn of others. My personal responsibility ensures that I live for myself and allow no one to live through me without my permission.
I would have to say dedication. If I am not giving a dedicated effort to whatever large or small task before me, I am not living up to my potential. I am, of course, more concerned about my dedication to the "big things" like my marriage, raising my children, and my career -- not necessarily to how dedicated I am to cleaning my house. But even if with that said, I really hate thinking "good enough" -- it always saddens me a bit when the reality of life is such that I can't give my best to everything I do. I am proud of my accomplishments, but I always see the room for improvement. I am most successful when I put forth the greatest dedication.
Integrity. Without it, everything that one has done in his/her life becomes a mere sham, a mockery of an authentic life. "At the end of the day" one always has to look in the mirror; after one is finished raising children, teaching children, working a job, what is left but the integrity of one's soul?
Nathaniel Hawthorne's exhortation in The Scarlet Letter, "Be true! Be true!" as the solution to a life without misery is, indeed, valid. For, even the old hypocrite of Hamlet, Polonius, knows this, although he does not follow his own advice that he imparts to his son:
...to thine own self be true,
And it must follow, as the night the day,
Thou cant not then be false to any man (1.3.78-80)
This is a question with many different potential answers. For me my most important value in life is my faith in God. I believe, despite what many intelligent people say, that there is a higher being. The ultimate questions cannot be answered by science, technology or anything else. From where did we come? Where are we going? What happens after death? Why should we live morally? These are all religious questions in my opinion, because they are based on faith. If a person is a scientist and tries to explain these question based on science, then that person has faith in science. This sounds odd, but science changes, old theories are discarded. Also new theories will emerge. And people, then, have faith that science will have answers.
I am sure that many people would disagree with me, but faith in a Christian God is for me paramount. There is another reason why. I believe that Christianity has a powerful explanatory power as well. There is comfort to know that there is a God.