And if you'd like to, state each reason why you gave it that grade
Microsoft: C+ It's a more of a personal since I'm not into many of the Xbox's franchises, but I have to admit that Microsoft showing just games is a huge improvement and at least one game interests me which is Scalebound.
EA: Didn't see it so I can't give it a grade. Though I will say a new ME is cool.
Ubisoft: B I haven't watched it, but my brother did so this is his grade. He told me it was mostly great until the end where they screwed up.
Sony: D WTF Sony? It started great with Destiny and then the conference just got boring throughout the whole show. It was very underwhelming. Not even the teaser with Uncharted 4 could save it.
Nintendo: A- Nintendo is like the the only company who understood what video gaming is about. From a direct with funny moments, great reveals and teasers and they still weren't done. There was the Smash Invitational which I loved and the Treehouse events, Nintendo just went nonstop with E3. I give it a A- because many of the great games won't be out until next year unfortunately. But still, I loved it and Nintendo easily won the conference in my eyes.