I would say Microsoft > Bethesda > Ubisoft > Nintendo > Sony > SE > EA. But anything below Ubisoft was awful, Sony was the worse presentation wise/style, EA was the worse in terms of boring.

Microsoft

I'd rank it as follows:

Microsoft
Ubisoft
Nintendo
Bethesda
PC
Sony
Square Enix
EA

Those are what I watched. Well have to watch Nintendo better when I get home. Didn't get ot watch it closely, some watch some just listen. At work on phone so...
All the hate to the 20 minute smash talk. I see nothing wrong with that. It's their big game, they tend ot do 1 big game each e3 for last few years. Second, i'll take 20 minutes of smash talk over 20 minutes of venue change like Sony, and third most Nintendo's E3's are like 20-25 minutes, so all the Smash was basically just a bonus. If they would have cut the Smash to a 3 minute trailer, that does not mean we would have gotten another 20 minutes of new shit, the conference would have just been 20 minutes shorter. People have to quit thinking doing one thing prevents another all the time.

Devolver was fun.

Microsoft owned E3 2018.

I just love their focus on games, games and games. Add in Phil Spencer and its just pure win.

40 games in 2017, 50 games in 2018 and I expect 60+ in 2019.

Microsoft has the edge but no one blew me away. As much as I like Smash, an E3 presentation is not the place to spend 25 minutes on one single game.

MS had the best show. It was indeed a great show for all players. In terms of exclusive games, however, nothing really changed.

Keyword here is "Good". Halo has been getting lower, and lower review scores for years now. Same with Gears. If these two franchises were anything other than FPS games, they would score in the low 70's on aggregate sites, but because the FPS genre appeals to so many people they get higher scores than they deserve. Forza isn't anything new. Just the same old yearly racing game. Might as well get hyped for Madden, Fifa, or MLB. 

Meanwhile Sony had Spiderman, The Last of Us 2, Death Stranding, Ghost of Tsushima, and Nioh 2 (PC/PS4 Only). 

So five unique and interesting games vs two boring shooters, and a sports title. 

Microsoft probably had the best overall show, but in terms of games most of the stuff they showed still gave me no reason to get their console since I can play all the stuff I was interested in on other platforms I already have. In terms of exclusives Sony wins, even though they didn't really show much new, what they did show of their games all looked really good. Nintendo was quite similar, showing very little new stuff, but the few things they did show looked good.

Ultimately, there were no truly great press conferences this year, but most of them were at least alright. EA's was probably the worst, Bethesda had a good showing, Ubisoft was decent, and Square Enix showed a lot of interesting games.

It has to be Sony, and I say that without caring about more than half their games. MS presentation was more about proving they're still in the game. Nintendo was about games releasing this year.

Real winner is CAPCOM.