my signature might provide a clue as to my opinion.
To me, success is:
Leading a meaningful life. It's not enough to be "happy" (whatever that means), to enjoy your work or circumstances, or to be able to consume experiences, goods, and others at a pleasant rate. In fact, these things often distract from real achievement. Happiness is a misplaced "right" that is often viewed as the end goal of all work, and we do ourselves a disservice when we make a fluctuating, internal, and subjective emotion our greatest good.
Success is about your ability to impact the lives of others in a lasting way, such that the chain reaction of the impacts of your having lived carry positive ripple effects to other generations. Your having lived should make others achieve for themselves and others significantly more than would have been possible had you never existed. We should all strive to be servants to others and stewards of the future, whether in our families, careers, or personal interests.
If, at the end of my life, if I can say that the way I lived communicated love, honesty, compassion, generosity, hope, and faith, and others saw this and chose that path for themselves where they would not otherwise have done so, I will consider that a success. The world is a house with many rooms in it, for all sorts of people and talents.
I can say that those who I admire most are people who give of themselves selflessly and generously, often at great personal cost. Think of parents of special needs children who pour out love abundantly to their children, priests and lawyers who fight for freedoms for others in situations of great oppression, people wrongfully punished by the law who peacefully protest and change their countries' laws through their perseverance, individuals who fight human rights injustices and face persecution for their opposition, people who consciously save and donate to the poor (even though they'd prefer a flashy vacation or a new car), people who help make others whole after trauma...
