I had this thought a couple of months ago when I was watching a documentary about some tribe in Africa. As it followed them on their daily lives hunting and raiding Bees nests for Honey, it dawned on me that these people aren't even aware of the things that most people would consider required to have a successful life. Nice house, lots of money, retiring or whatever. To them, a successful life is probably just surviving from one year to the next.
Does your culture define your own personal meaning of success? I would imagine it has something to do with it. But for humanity as a whole...?
I still dont know the answer but I'm pretty sure that happiness has to be in there somewhere.