I feel like I shouldn't expect anything because so many reveals have happened already. For example, Sony announced LBP2, Killzone 3, and now infamous 2 before E3. Their big hardware reveal of the Move was also a few months back. There is definitely going to be a lot of (shovelware) software there for the Movie that'll be new, and hopefully the rumored Ape Escape that uses it, but those are the types of games that seem like big reveals. A rumor that gets often mentioned is the PSP2 and how they may, or most likely may not, show it at E3 due to the 3DS. I don't even know if the 3DS is confirmed to be shown at E3.
There are still a bunch of games I'm looking forward to seeing. This is the first year in a while that I'm looking forward to Nintendo's the most considering they have the best chance of showing new hardware and a new Zelda. Brandnew reminded me of Epic Mickey and that's a game I hope is good. Really want to see Vanquish in action. Want to see how LA Noire and Agent are turning out now that Rockstar redeemed themselves for me. Deus Ex 3, Metal Gear Rising, hopefully a sequel to Banjo Nuts and Bolts, infamous 2, etc.
Also, I agree with Eel about wanting to see reactions this year. Between Natal, Move, and 3DS, there is going to be some scorched earth stuff on gaf.