I'm definitely looking forward to Nintendo's presentation. Wii U info (console specifications, price, release date, actual game announcements), new 3DS announcements, dates for previously announced 3DS games (Luigi's Mansion 2, Paper Mario)... It should be a blast to watch. I'm also really hoping that the rumor of Retro Studios making a Star Fox+Metroid crossover game for Wii U is confirmed there (*EDIT* this rumor was debunked, sadly).
My biggest hope here is to see Nintendo reviving the Star Tropics franchise, but I don't think that's possible
Sony's presentation HAS to be good, otherwise Sony will be in big trouble, or at least worse trouble than they currently are. I really want to see a lot of Vita stuff announced, and dates/announcements for some PS3 stuff. I hope the presentation will be 100% about games, no BS like that dumb Kevin Butler part 2 years ago. I don't think they'll show off their next console yet, but I kinda hope they tease it at least. This is actually the only presentation I'll be seeing live, the others happen during my work hours.
For Microsoft... well, they already said that their presentation wouldn't be about games, so here's exactly what will happen: 5 minutes of Black Ops 2, 50 minutes of new services and features for XBL as well as Kinect games no one wants, and 5 minutes of Halo 4 at the end. They'll be the laughingstock on the conference as they were the last 2 years.
Beyond the presentations, I just hope to see a lot of gameplay for a lot of games, and a lot of dates for said games.