Gonna go with Microsoft. Sony had a lot of surprises and and Nintendo gave me a few games to add to my Wii U/3DS list, but ultimately Microsoft just gave me more reason to care about the Xbox One and, really, anything Microsoft. I don't particularly hold the company in high regard, if I'm to be completely honest, but the Augmented Reality was pretty cool and the conference allowed my to once and for all say goodbye to my dying Xbox 360, giving worth back the my (and many others') 360 games and ultimately giving me a reason to use the Xbox One. Similarly, it gave me a reason to actually recommend the system, especially for 360 owners.
For Sony's, I didn't really feel more enticed to buy a PS4 after it due to a lot of the games coming out on PC, and after finding out that The Last Guardian is being finished not out of desire but because of contractual obligation, I'm more looking forward to the other projects that will be coming out from them and can wait on TLG despite having waited so long for it. It had a lot of shocks and hoorahs, but it also had a lot of "First on PS4s" and available elsewhere's that made it better for me as a general gamer than a Sony consumer. And the supposed "In memoriam" to the Vita, that. That happened. Can't say I was particularly happy.
As for Nintendo, again, it gave me some games to add to my already large "to buy" list for the Wii U and 3DS, but I'd be hard-pressed to say that its conference was on level with MS'. Its Treehouse, on the other hand, did a fantastic job of showing off several games for Nintendo's consoles, with a notable example being the previously mysterious Genei Ibun Roku #FE (SMT vs. Fire Emblem) which now has a plethora of gameplay footage on display.