[Never got around to watching Bethesda's, so I won't be scoring that one]
EA - 6/10
Aside from some of the most hilarious and cringey public speaking faux pas I've ever seen in one conference, the reveals and games shown off really weren't bad. A Way Out was a tremendous standout, Battlefront looks excellent, NFS looks pretty fun, and there was a semi-interesting tease for Bioware's IP. There was no final reveal though (I was really hoping to see more of Visceral's SW game), which was a bit disappointing. Plus there was way, way too much filler. Overall I'm glad I tuned in. If nothing else, watching the YouTube guy freeze up was comedy gold.
Xbox - 4/10
This conference had its moments, but it was also very emblematic of Xbox's problems at the moment. While the One X looks sleek, the game premieres did nothing to sell their new box. Not when you consider how many of the games shown were timed exclusives, how many were multiplatform, and how few were first party. What does an Xbox One owner have to look forward to that no one else does? I mean, apart from the couple of console exclusives and some timed ones? That's the question I went into this conference with, and I don't think Microsoft did a very good job delivering the answer to that question.
Sony - 6.5/10
Not every year can be a megaton year, and I completely understand that. Even so, it's hard to ignore the fact that this conference could have been so much better with better planning. So many great games, from Undertale to GT Sport to Ni No Kuni II, were wasted on the pre-show while the actual conference was left with a horrible snooze fest of a VR segment. Had they swapped the VR portion with all of the pre-show announcements, I think Sony's conference would've been much, much better. Obviously after Sony's last couple years it's hard not to be disappointed.
Ubisoft - 8/10
Ubisoft did a killer job just making me smile. The Crew​ 2 looks fun, Mario + Rabbids looked surprisingly good (and of course Miyamoto and Yves having fun on stage was a blast), and even Assassin's Creed looks good this year. The fact that they've barely even started Beyond Good and Evil 2 puts a little bit of a damper on that announcement, but it was a cool surprise nonetheless. I never thought I'd say this about an Ubi press conference, but... Well done, Ubisoft.
Nintendo: 8/10
Nintendo conferences tend to completely bomb just as often as they impress, but they had a pretty slick presentation this year. In my 20 years as a gamer, I don't think I have ever shouted, smiled, and laughed at a trailer as much as I did with Super Mario Odyssey's. That game single-handedly made up for Reggie's nonsense philosophical ramblings, the complete lack of anything for Metroid Prime apart from an announcement, and more paint-by-numbers Kirby and Yoshi games, so soon after we've already gotten games in those franchises. Prime 4 was a killer announcement despite the lack of trailer, and the fact that they're even developing it at all, despite the series' weak sales, shows that Nintendo isn't completely tone-deaf to what its fans want. And that was a real worry after E3 2015. Overall this year's presentation signaled that Nintendo has learned a lot of tough lessons after the Wii U, and it's clear they're ensuring that the Switch is a robust platform going forward.
Edit:
Overall - 6.5/10
This E3 was overall pretty underwhelming. Microsoft and Sony both were disappointing. Nintendo and Ubi were the highlights I think.