The search engine giant's social network debuted on the pyramid this year and came out joint top alongside Wikipedia with a score of 78 on a 100-point scale.
Facebook scored 61, an 8% decline from the previous year, ranking it below the likes of Twitter, LinkedIn, Pinterest and the Google-owned YouTube.
The research was conducted in conjunction with ForeSee, who pointed out that Google+ scored higher than Facebook because it has no traditional advertising, is secure, and offers a better mobile experience.
Facebook users' most common complaints include advertisement and privacy concerns, along with frequent changes to the interface.
"Facebook and Google+ are competing on two critical fronts: customer experience and market penetration. Google+ handily wins the former, and Facebook handily wins the latter, for now," said Larry Freed, ForeSee's president and CEO.
"It's worth asking how much customer satisfaction matters for Facebook, given its unrivalled 800 million user base. But I expect Google to leverage its multiple properties and mobile capabilities to attract users at a rapid pace.
"If Facebook doesn't feel the pressure to improve customer satisfaction now, that may soon change."
Social networking media companies have some of the lowest user satisfaction ratings on the index, with the industry's average of 69 being only marginally higher than beat airlines, subscription television service, and newspapers.