Joey may not be book smart...

...but I would argue that he's the most emotionally intelligent friend in the group.

He's endlessly supportive, always there to cheer them up when they're down, always down to brainstorm solutions (even if his ideas aren't the most practical), does his best to avoid hurting anyone's feelings... He goes above and beyond for everyone he loves.

I don't even know if I think that was an intentional move by the writers, but every time I rewatch the series, his emotional intelligence becomes more and more obvious. He consistently goes out of his way to make sure everyone in his life gets what they want and need.