Getting in on this conference hype list:
1. Square Enix - as far as I'm concerned, SE has the best line up of known games; Deus Ex: Mankind Divided, Dragon Quest Heroes, Rise of the Tomb Raider, Star Ocean 5 and the Kingdom Hearts HD Collection which some posters in this thread have hinted at. If they announce new entries in older IP's (preferably Parasite Eve) or, God willing, a new game by Taro Yoko (doubt this, but I can dream, right?), then they'd win E3 in my eyes.
2. Sony - I spend most of my gaming time on PlayStation platforms, so this should come as no surprise. I generally love Sony's first part output - though they'll have to show off some compelling content this E3 as I've found most of their output to be lacking this gen. Horizon, Tearaway: Unfolded, Until Dawn, Uncharted 4 and hopefully Gravity Rush 2 are what I'm most looking forward to. My dream game from Sony is them bringing Dylan Jobe on stage to announce a Warhawk/Starhawk sequel. Sony usually has an amazing indie showcase as well.
3. Nintendo - Once again, the big question mark of E3. Nintendo has plenty of games I'm interested in - Devil's Third, Mario Maker, Yoshi's Woooly World - and almost always has some awesome surprises. Excited to see what they have planned for this year.
4. Bethesda - Surprisingly, I'm not that hyped for Fallout 4 or Doom. It's the potential Dishonored 2 and/or Dishonored: Definitive Edition that I'm most excited about. As well, I've liked that Bethesda has shown a commitment to traditional single player experiences (The Evil Within, Wolfenstein), so I'm hoping for some new developer partnerships from them.
5. Ubisoft - Normally Ubisift would be at the bottom of my list, but with Rainbow Six: Siege and The Division coming out, I find I'm more interested in their conference compared to previous years. Hoping for a new Splinter Cell or Ghost Recon. I'll probably just tidy up around the house while they're talking about Assassin's Creed.
6. Microsoft - Unfortunately, I'm not too excited for Microsoft this year. We'll likely be seeing Quantum Break and Halo 5 again, which have lost their novelty despite looking awesome. Crackdown could be good if they decided to show it; Scalebound will likely impress as well. It's a shame the Gears remaster was leaked, as that would have been a nice surprise.
7. EA - I find it hard to get excited for EA's conferences anymore. Looking forward to some Battlefront footage, but the absence of Clone Wars/Prequel era content has diminished my hype. Garden Warfare 2 will no doubt be good, and hopefully we'll finally get to see the new Mass Effect. Other than that, not much I care about unless they announce a new Dead Space.
8. PC - This is only at the bottom of my list because I don't actually know what to expect from it. Is it mostly going to be multiplatform games? Hopefully we'll see some of XCOM 2 and Beyond Earth: Rising Tides, otherwise I'm not sure what surprises there could be that wouldn't already be revealed at one of the other conferences.