I think it'll be close between Microsoft and Nintendo..
In 2006, Iwata had a keynote at GDC. He announced a brand new Zelda title for DS and he announced third party support for the Virtual Console among other things.
At E3, Nintendo stole the show with a showing of Wii Sports, an early Wii Music, Super Mario Galaxy, Metroid Prime 3, Super Smash Bros. Brawl announcement, Zelda: Twilight Princess Wii gameplay and demo, Excite Truck, Project HAMMER, Disaster: Day of Crisis, FF: CC, Red Steel etc etc..
The year is now 2009, Iwata had a keynote at GDC. He announced a brand new Zelda title for DS and also a new Vitual Console Arcade service and a long awaited Wii storage solution.
E3? Well I don't think they'll show Zelda Wii.. but they'll have Wii Sports Resort, Pikmin 3, a new EAD4 title, one of Retro's new titles, a new NST title, Zelda: Spirit Tracks, Red Steel 2, Grand Slam Tennis, etc..
Microsoft have a lot of games they COULD show and Sony really don't have many suprises.. It'll mainly be games that have already been announced so I don't see how they will 'win' but who knows what may happen..
