They are still out there, and seem to be purchased and enjoyed. A Target store I visit from time to time has maybe 25 feet of shelf space devoted to them. That's been so for several years, and with shelf space being so hotly battled for by manufacturers, I think that the board games still sell well.
BTW - Monopoly is a well-studied game. Here is one of many references:
http://www.tkcs-collins.com/truman/monopoly/monopoly.shtml
The out-of-print text, T.H.E. Ultimate (Wm. Poundstone, Dell/Doubleday/Bantam 1990, ISBN 0-385-24270-0) has an interesting chapter, too.