I think there is still a potential in Google Adsense if you have a large number of sites, havine high traffic on them. Google has been hard on publishers with slim websites content and no value at all, and started banning them. Asian countries were the most targeted ones in this spree.
I think, if the sites you have are good enough, have value for the visitors and getting some decent traffic, i think Google adsense still got a chance to make you recurring money. I'm a gainer, but don't put my efforts into adsense for pennies, i like to make big money and believe me there are ways to make big money e-g affiliate marketing, web development and flipping it for cash etc.