On the suitability of Free2Play for different games

Imagine a fantasy game in which you have a hero who is exploring single-player dungeons, and finds decorative items there. The purpose of the game would be to build the most beautiful city. It isn't hard to see how a Free2Play business model would work for this game: Buy decorative items to further make your city more beautiful, or buy access to new single-player dungeons. Somebody spending a lot of money would have a prettier city, but except for possible jealousy that would not have any negat

World of Warkraft...