The first press presentation was Microsoft early on monday (in LA anyway) where Halo 4 gameplay was shown and SmartGlass was officially revealed. The new Splinter Cell, Tomb Raider, and Gears of War games were also shown along with a small number of Kinect games too.
Electronic Arts was next, announcing their newest games. Although there were no new intellectual properties, the new Medal of Honor and Crysis games impressed with their stunning graphics. EA also announced a partnership with UFC, giving EA the exclusive rights to making the next several years worth of Ultimate Fighting Championship games.
Ubisoft's presentation, hosted by Aisha Tyler, was almost unanimously voted the best of the bunch. With the stunning new IP's Watch Dogs and ZombiU, and much anticipated games like Assassins Creed 3, Far Cry 3, and the new Splinter Cell, Ubisoft came out swinging in this very games oriented E3.
Sony also stepped up their game with two brand new IP's of their own in Beyond: Two Souls and The Last of Us. God of War: Ascension and PlayStation All Stars Battle Royale solidified their games line up for the PS3. A little (literally little) love was given to the Vita and Sony also announced and demoed the Wonderbook.
Last, but certainly not least, came Nintendo's presentation. Most were clamoring for any info they could get on the WiiU, and Nintendo gave a decent list of some games to expect. Pikmin 3, Super Mario Brothers U, and Rayman: Legends were some of the expected announcements, but ZombiU and Lego City Undercover were generally the talk of Nintendo's presser.
Thanks to IGN for posting all the press conferences in full on youtube, subscribe to their channel for more E3 news.