This is one thing that bothers me about Zynga et al. The entertainment business has always been like this, you can't have a movie run in the theaters for years on end. I don't think why they think a game will work differently if the put enough analytics in it.
You can't have the same movie run for years (well, unless it's Rocky Horror), but you can have the same premise. In the same way you can have the same kind of game (Farmville -> Cityville, etc etc) but with a different setting, look, etc.
