THe Wall Street Journal ran a "symposium" on this question last week. Several writers contributed, but the closest thing to a sensible answer came from Ed Husain, who had once been seduced by Islamofacism, but has since reconverted to Islam. There is no such thing as "moderate" Islam. There is just Islam. So-called "radical Islam," or "political Islam" are misnomers for the ideology believed by Osama Bin Laden and his followers, wannabes, and hangers-on. The most accurately descriptive name I have heard for it is Francis Fukuyama's term: Islamofascism.
Islamofascism denotes an unholy union between one strand of Islamic Salafist thought and Western European Fascist thought. Ed Husain describes this in some detail in his memoir, The Islamist, which I have reviewed here.
Now, if you're wondering what will eventually defeat Islamofascism, the answer is Islam. Or if you must have an adjective, authentic Islam.
The use of the words "moderate" and "radical" connote that Islamofascism is simply a more intensely believed version of Islam. Nothing could be further from the truth.