There is an excellent thread over at WebmasterWorld named What kind of site does it take... What kind of site does it take to make a enough money from AdSense to live your life?
The first response is "The key is really the domain names and not the website, especially during the early stages." But it is quickly argued on. Google's AdSense department is quick to review and boot many sites that participate in the program that are not up to their standards.
There are many ways to make money with adsense. I know people that have a "search engine" that is simply AdSense driven. I know others that buy misspellings of popular domain names and throw up AdSense. I know some that build up huge content sites. There are many ways to make for a successful AdSense site.