Without a doubt, blue zoo.
Following blue zoo, I would rank them: Flying Fish, Fulton's, Narcoosees, Coral Reef and then Cape May.
blue zoo is not on the dining plan and has a pretty adult atmopshere. Fulton's is also not on the dining plan. Flying Fish and Narcoosees require 2TS on the dining plan. Coral Reef has the amazing wall tank but has a limited menu, slow service and it can be noisy. Cape May is a buffet.