Game creation isn't something most people want to do. Building maps and towers seems okay, and customising characters, or maybe designing a car paint job. But the idea of a game creator as a product is probably doomed to financial failure because it's so niche. A game that allows the 0.1% interested in taking it further to take it further is the necessary design objective if one wants to get people creating games. Unless the tools are mindnumbingly simple, like drag a thing onto a thing and the system automatically makes it behave how the user wants. 
