I enjoyed Microsoft's the most, but in terms of who actually promoted their console and company the most and best that's Sony, easily.

Sony easily won! Easily won! Final Fantasy XV and Kingdom Hearts III confirmed for PS4 alone was enough for them to win (exclusive or not), but add to that the fact that the PS4 is DRM free, does not require an internet connection, and is only $399 and Sony triumphs over Nintendo and Microsoft. Nintendo comes second because of the X trailer they showed. Also Mega Man in Smash Bros. is cool. Then Microsoft is third with D4 probably going to be excellent, but I will not be getting an X1 ever at this point.

Microsoft- had a nice conference.
Sony- was ok, but the last 10-15 min, damn, oh ff 15 and kh3 were shown too
Nintendo-didnt see it, but seems lackluster by reactions
ea-battlefront, enough said xD
Ubisoft-cool new ips
Overall sony, I would say

Square Enix.

http://gamrconnect.vgchartz.com/post.php?id=5288528

I would have said this if the thread was just asking who won E3 instead of specifying Nintendo, Sony, and Microsoft.

haven't seen the nintendo conference

Sony won without question (thanks to Square Enix). I'm not buying a PS4 because I don't want to be locked out of online multiplayer for not paying a subscription, but I can still clearly agree that Sony won.

Sony's had the most epic and memorable moments.

They all were very good, and I rated them all very similarly.

There were good parts and bad parts in each conference. As such, I say the winner is the gamer.