I would say Nintendo. I honestly expected Nintendo to take the prize of best E3 with Microsoft in second and Sony in third. But I think Microsoft dissapointed me as much as Nintendo did in 08/09 and that is unexceptable. Then again I predicted that PSP2 was going to be at the Sony conference so I guess It would have been close if Microsoft had actually shown some quality software. The quality software present Gears3, Fable3 and Reach were both given minimal showtime to make room for the wreck we call Kinect.
I had hoped Rare's big title was a Kinect Banjo, I thought for sure that their would be an announcement of Gears using Kinect as an option. I thought Microsoft would throw its weight behind it. Instead Microsoft offers a few Wii rip offs instead of quality new software. Seriously the title I was most exited for was Kinectimals. What the heck is with KinectAdventure it looks like a MarioParty mini-game.
Seriously though Nintendo can't loose this year. They need to be king. With Zelda Wii, Pikmin Wii and Retro's new game they will have at least as many hardcore games on Wii as Microsoft's providing. Then theirs the Ds we know of big games like Golden Sun and Sonic Colors but what about all the other games...then theirs 3DS which needs launch titles meaning more quality software.
If Sony reveals PSP2 they could give Nintendo a run quantity wise but Nintendo just makes higher caliber software.