Microsoft were working on improving the Kinect and developing more Kinect compatible games. They showed family-friendly games such as "Sesame Street: Once upon a Monster" and "Disneyland Adventures", both co-op games. They also showed how Kinect can make a photo of a person and turn this photo into a 3d avatar. The same can be done with objects like plushies to bring them into the game.
"Ghost Recon: Future Soldier" will use Kinect to fire a weapon by doing a motion, like you're actually holding a weapon. I find it difficult to explain, so I will show you a video of it instead:
I think it looks quite interesting, but I am not sure if aiming a gun like this wouldn't be too difficult.
Furthermore, Microsoft unveiled the new Halo 4, developed not by Bungie but a different team. They only showed the teaser so we don't have too much information about this. They also plan on re-releasing Halo: Combat Evolved in HD, with fully upgraded graphics!
Another game is the new Gears of War 3, where they delivered a gameplay demo during their conference:
These were the big highlights for me! Stay tuned for the other developers' summaries!