In Centesimus Annus, Pope John Paul II claims that the desire for personal possesions is not a sin, but the desire to take from others is. If you feel inclined to acquire a new house or boat or car and that desire drives you to work harder then it is good. However, if the desire drives you to cheat or to take what is already the property of another then it is of sin. However, the Pope does add that wishing to elevate yourself above others is a sin, and that doing so by acquiring things of social value is in violation of the comandments. Col 3:23 states - work hard and carefully, at everything you do, as though working for the Lord and not man. This is just the teaching of my own personal faith, but maybe that can shed some light on the feelings of a large group of Christians.