You have, as countless others, mixed up visibility with optical power. The only reason 532nm appears brighter is because our retinas are more sensitive for that wavelength than 650nm. End of story.
Altough I don't blame you, because loads of companies sell green lasers on the internet. Many of them are unexperienced with lasers, and says stuff like "green laser - much more powerful than red laser." Because of this, many people believe that this is the case.