Prince of Persia
This is the best looking game of E3 to me. Of course there are graphically superior games in a technical sense (if you haven't done so yet, check out Far Cry 2), but nothing quite caught my eye like Prince of Persia. It's hued like a Final Fantasy game, but cel-shaded and uber-detailed.
If it actually turns out to be Okami meets Ico, well, that would be a hell of a game.
We may have seen PoP in the months preceding July, but Fat Princess is, I think, newly announced out of L.A. It's a multiplayer game based aroud capturing the other side's princess while defending your own, a.k.a. capture the flag. The differentiating factor here is that in most ctf games you can't fatten up your flag(and slow down those trying to take it) by feeding it sweets found around the map. Another difference between Fat Princess and most capture the flag games is that it's not a first-person shooter. The game uses an isometric view, and the character classes and gameplay seem to complement it well. Swordsmen are basic soldiers, who can pick up various weapons and are your frontline attacker and defenders. Priest heal allies and can buff swordsmen a la TF2, while mages use magic offensively against multiple enemies. The builder harvests resources around the map to create more buildings and defensive structures. In fact, he has a tech tree to do this, eventually leading to offensive weapons like catapults. All that in a 16 on 16 game sounds like hysteria.
I Am Alive
I Am Alive is set in Chicago after some as yet unknown disaster. Not much is known at all about this title, other than I want to play it. The only downside to this game so far is that the main character kinda looks like create-a-wrestler guy.
Hopefully there'll be more later this week.