A number of indie developers banded together to declare that today is "Size Doesn't Matter Day." The objective: Dispel the myth that a game has to have 40+ hours of content to be fun. And while I have quite a bit to say on this topic, I think that my fellow indies have already covered it quite thoroughly, so I'm going to tackle it from a different perspective.
If you're a game developer, the truth is that there are simple things you can do to extend the replay value of a game. Here are a few tips: