Nintendo's E3 2019 was incredible.

Nintendo's E3 2014 Digital Event. The Robot Chicken skits, the awesome wuxia/anime duel between Reggie and Iwata, Splatoon and Breath of the Wild reveals, etc...

https://www.youtube.com/watch?v=GisRY6h100U&t=683s

Will never be topped...

Keanu Reeves appearing to promote Cyberpunk 2077 is a modern classic.
God of War 2016 demo, the reimagening of the franchise, also comes to mind for sweetest moment.
I am still fond of the Uncharted 2 presentation with the falling building and Nathan Drake inside of it.
Uncharted 4 had the awesome chase scene demo at E3 2015 I think.

For my overall favourite E3 I will go with 2016 than. God of War, Death Stranding, Horizon, Spider Man, Resident Evil 7 (VR aswell) - as someone above already said, the Sony conference was legendary.

I can't remember a single MS or Sony conference since 2005 or 2006. They are so forgettable to me.

Riiiiiiiidge Raaaaacer!

Haha, yeah, I forgot about that one.

Yeah Nintendo's best E3's in recent years was 2014 and 2019. 2014 had Bayo 2 and Xenoblade X. That alone is a winner.

The 2017 Nintendo Direct when they finished with Super Mario Odyssey. It went instantly from what seems to be a great game to an instant classic and masterpiece.

Never hyped before and after for a game at this level