For the moment, nintendo. I couldn't watch Sony's because I wasn't near a computer at the time. Microsoft's was too cheesy, what with that dialog between the two girls with Natal (yes, Natal, not Kinect, I refuse to use that name). I also hated the little kid with that tiger. It was too cutsey wutsey, and if you look closley, the hands on the screen petting the tiger, don't resemble the little girl's movements at all.
Nintendo had the most entertaining conference for me. I enjoyed having Miamoto himself showing us the new Zelda game, and that little entrance he did made me smile a little.
Also, nintendo announced the most games out of the three of them.