From social media consultant Jason Falls comes this chart illustrating reception of major burger brands in social media based on volume of conversation, sentiment, and passion, using data pulled by ConsumerBase. In-N-Out had the most volume, but came in second for positive chatter right behind Five Guys. White Castle was the most polarizing between love and hate, and Wendy's was most disliked, although not passionately so. Read more at Falls' site, Social Media Explorer.
As pointed out in the site's comments, this chart is inconsistent for combining burger chains with specific burgers (Whopper instead of Burger King, Big Mac instead of McDonald's), but it gives a general idea of what people think of burger brands.