Consumerism and personal fulfillment

For most of us living in the Western hemisphere, living conditions have never been better. Even the lowest social strata have access to technology and medical care that Royalty couldn't conceive of 2 generations ago. Yet many of us seem dissatisfied with our lot, live with the perpetual notion that we're missing out in some way.

Why is this? Sure there are obscene levels of inequality in society but why should be use the assumed happiness of others as a barometer for our own fulfillment? And how have we come to connect success with the size of our bank balance?