I'd say nintendo, but not by much. That's me being objective since I'm not swayed by any of the nintendo titles, even pokemon.

Sony's titles are way more appealing to me but so much of it is on 2018 and while there are some cool titles coming this holiday, it still feels dry.

I don't care about MS's titles and I specially don't care for the XBoneX. Any games that i did take interest in (cuphead and the last night) are on PC so I don't need an xbox

Overall, I feel very underwhelming by E3 as a whole.

EDIT: It just hit me that Nintendo just needed to announce two titles, with nothing to show for, to win E3. That is a very, very low bar for all companies.

Nintendo by a long shot, but it was a pretty weak year. I'd say depending on footage next year of some of the announcements, Nintendo has a good shot next year as well.

Apparently all it takes is words to hype them up. lol

As a Nintendo fan, I think Nintendo won

Not super good though, since this year's conferences were all not that great

Personally I'm torn between Sony and Nintendo, mostly for the latter odd pacing and title only announcements.
Maybe Nintendo by a smidgen, feel it lacked a real defining moment. Then again, Mario, Kirby and Yoshi.
Overall:
Ubisoft > Nintendo ≥ Sony > Bethesda > MS > EA

Sony for me. Almost every game they showed I want. (aside from the VR)

Nintendo and Ubisoft. Sony was decent too.

Gotta give it to Nintendo. If they had shown Metroid Prime 4 it would had been a crushing victory but now they just barely won.

I'd say Nintendo. I feel like all three of the console makers have had a pretty underwhelming E3s, but Nintendo's at least had some announcements. The main ones were about as vague and noncommittal as possible, but they were announcements nonetheless.

Definitely Nintendo.