The level of consistent quality in the conference would make it number 1 for me.
Kojima was a megaton (Given the resistance to even just the IDEA of Kojima appearing at MS E3, let alone a new Metal Gear Solid game).
That Milo tech demo was astounding. Let's not think about games and think about pure tech, that was brilliant. Surprised to see it at E3, looked more like a CES thing to me (especially given that much like the Wii mote, it'll excel at certain genre's and be complete failures in others).
If you thought MS conference was not outstanding, you're clearly a Sony fanboy. They showed everything they needed to show (ODST, Wake release date, Conviction release date, new halo, Forza 3, Crackdown 2), those alone would have made a good conference, but they went above and beyond that. Acknowledge the hardwork and greatness of the conference, and hope that Sony will be better.
I really hope Sony pulls a big showing. I would say nearly all the wind generated by KZ2, Infamous and all these pre-E3 announcements might be taken out of their sails by the end of the week if their E3 isn't as big. Sony, no one cares about interpretations of sales numbers, we care about games. Bring It.