Interesting that 2016 and 2018 got votes in both the "Best E3" and "Worst E3" thread.
Quite divisive and controversial shows those two.
2016 is about what you think E3 is for I suppose. They presented what they wanted to present very well and it was very effective. It was also almost entirely one game.
2018, it's literally a matter of whether you like Smash. It had some good announcements like Dameon X Machina (which I know wasn't dynamite at launch but was a very cool surprise at the time) and Super Mario Party being the first good MP in ages. And the DLC for Xenoblade turning out to be as massive as it was. And some cool third party announcements that unfortunately got leaked. But there's no getting around Smash being so much of the show.