If you can be sure which idea is going to be most marketable, then that may be one way to decide. One of the advantages of the e-publishing market is that you can publish information for a particular niche very economically. Try to spend some time researching your market to make sure your book will be similar enough to the other offerings while being different enough to be distinctive. For instance, the romantic comedy where the couple doesn't actually end up together may be creative, but may not garner you many fans.
Another way to choose might be which idea has a message that you think is most important. You may choose an idea with a message that you are passionate about over an idea that is funnier or more creative. The trick is talking about your passion without getting "preachy".
As for Broken Toys: China's Song, I chose to write it over a notebook full of other ideas for one reason: the characters would not leave me alone. Any time I let my mind wander, it would wander into their world and I would learn a little more about them. A cast of characters that are original, funny and creative, will always make a lesser idea better than a great idea with two-dimensional characters that the reader has a hard time caring about.