I'm going with Microsoft. I think they have their backs against the wall and they're going all out. They're going to spend a LOT of money and they're going to try to make this their best E3 ever because they're desperate. We're going to see Halo 5 footage which will blow people away and we're going to see snips of some of their other projects.
Sony has the most potential here, I think, but since they're in a good place, I don't think they'll rush. They have a TON of projects they could show off but I get the feeling they're not going to push them out early just to build hype. I hope I'm wrong about that.
Nintendo could do some damage with a crowd reaction for Zelda but obviously that won't happen. The gamer-journalists would go nuts and create a great atmosphere so that's a shame. Still, Zelda plus Smash Bros footage would be a great foundation. One or two big surprises and they could pull this away from Microsoft, though I don't even know if they HAVE those surprises. Showing more footage of games that have already been revealed won't do the trick and titles like Bayonetta, X, and Hyrule Warriors aren't very big to begin with.
My predicted order of finish:
1 - Microsoft: Desperation + Halo + lots of money.
2 - Nintendo: Zelda + Smash Bros. + plus a big surprise and they could take the top spot.
3 - Sony: They could contend if they trotted out all their projects but they're not under pressure to do that.
