I think it depends on where you are. For someone who doesn't have very much money, suddenly coming into a large sum of money would make them quite happy. They could get all the things they so desperately want/need. A car, a house.... and they would be happy. Those who already have money and are unhappy due to something, well obviously money won't solve their problems.
I know very well that money would make me and my family very happy. We would finally be able to rise above this dreaded poverty line and not live in such anguish. We're all miserable with our current state of affairs, and most of our "plans" have money involved. So it isn't so much as having money, but being able to get what you need with it that creates the happiness.