If you directly compare metrics like CTR and CPC, often Facebook Ads effectiveness seems far inferior to what can be achieved on Google Adwords search network and other search engine advertising platforms.
Conversion and click through rates on Facebook are more similar to those you can get with banners on content networks. Apart from the fact that Facebook Page ads and Event ads can be seen by friends when users Like them, the difference between ads on Facebook and ads on Google lies in the targeting system.
Two different targeting systems
On Facebook you can choose the audience for your ads. Targeting options allow to filter users based on interests, demographic and geographic filters: You can reach the right audience and your ads will be seen only by users you have profiled.
Google instead, doesn’t trigger ads based on what users “Like” on Facebook or their Facebook profile information: Search terms typed by users trigger relevant ads. On the Display Network ads are shown on pages with related content: Google understands what the page is about and matches ads accordingly. In both cases, you have to bid on keywords, and you have no control on who is going to see your ad.