Monopoly Alternatives
Settlers of Catan
For adults, I would suggest Settlers of Catan, since it's a much better game to me and a lot more fun to play.  If your willing to play a full game of Monopoly, then Catan is a prefect fit since it's actually shorter.  There's also a much more nuanced trade mechanic, and a board to stack our your share of.  I see it as a great chance to introduce them to Euro games if they haven't played one before.
For young kids, if they want to play Monopoly, I wouldn't dare be a spoil sport and suggest something else.