None of them really have. In fact the one i'm most hyped for currently is Microsoft's, since they keep talking about how this E3 for them is going to be the best first-party wise and games-wise and that apparently they have so much to show that they can't even fit it all into E3 and have to save some for Gamescom.
The rest is mostly just based on hyped assumptions. Sort of like how Bethesda is having a conference and everyone is getting hyped for Fallout 4. (Don't get me wrong, I hope Fallout 4 will be announced as well and think it probably will be, but at this point everyone is just assuming it and nobody can be certain).
Either way in general I don't think E3 being "not worth watching" makes sense really considering it usually is where most of the big games are announced. It's at least still an exciting event.
