Among the many cool things Nintendo revealed at E3, Kirby's Epic Yarn is one of my favorites. I am not the biggest Kirby fan in the world, but the game's incredible art direction nearly demands a purchase on looks alone. Nintendo gets mad props for their E3 presentation, which treaded familiar ground (as usual) but also offered some neat surprises. And not a space marine in sight.
On the other hand, Microsoft had a strong showing but spent way too much time on their extremely underwhelming (and derivative) Kinect software. The only thing that really has me interested is the "Your Shape" fitness game from Ubisoft, which seems to do some very cool things with the skeletal/body recognition capabilities of the Kinect device. Sony sort of landed between the two, in my opinion, with an entertaining (but way too long) presentation that focused heavily on 3D gaming. Seriously, Killzone 3 looks (graphically) fucking unbelievable. And the Move stuff appears to be a lot more creative and interesting that the Kinect games. Though Kinect seems to be more of a technical marvel than Move, Sony's conference proves that it's really all about the software.
So if I had to rank the "big three" presentations at E3, I would give the crown to Nintendo, followed by Sony and then by Microsoft.