2016...maybe not the best E3 overall...but they did something not only that no one had ever done before, but also something that many people thought was a recipe for disaster. They put all their eggs into the single basket that was Breath of the Wild...and blew everyone away. Their E3 was a success on many levels and started a hype train we had not seen for Nintendo in a long time with just a single title. Everyone went in expecting to be let down, but when it was all over most people were just amazed at how they pulled it off.
(I voted 2017 in the poll by accident 😑)