EA: C. It was a mess, but A Way Out and Anthem were pleasant surprises.

MS: C+. Microsoft ain't learned much, but they showed a grip of (not exactly exclusive) games. The plus is for the One X box being hella slim and sexy.

Bethesda: B-. Evil Within II looks nuts but I'll never play it. Wolfenstein II looks nuts and I can't wait.

Devolver: A/F. What the fuck was that?

Ubisoft: B+. Beyond Good and Evil 2 is a beautiful CG trailer.

Sony: C. They ain't really annouce shit. They just teased us with dope footage of games we already know is coming out sometime in the 2030s. The hot streak is over. Woulda been C- for the disappointment, but dat Shadow of the Colossus remake tho.

Nintendo: B+. Metroid Prime 4 is a promising title screen. Woulda been A+ if we actually got a trailer. Woulda been A++ if they announced Metroid V instead.

EDIT:

Nintendo gets bumped up to A- because they announced a Metroid II remake for 3DS.