The Unreal Tournament 2007 demo made my breathing stop for a second... literally. In a show dominated by games that all LOOKED visually impressive (even 3rd-string games all use advanced shaders and bloom effects it looks like), UT07 stood head and shoulders above anything and everything I saw.
As for sheer uniqueness, Spore looked like the most creative thing at the Expo, although I worry how much "game" will be in there. But I felt that way about the Sims as well (still do, in fact), so... Either way, I predict that Spore will either totally redefine the simulation genre, or create some totally new one when it comes out.
Fury from Auran looked fun and we had a blast playing PvP in South- look for a developer interview, exclusive screenshots and a E3 preview in a few days. The Conan MMO was surprisingly polished as well, and actually has me looking forward to a betas invitation (if we get one).
And Company of Heroes, from Relic (the guys that did Homeworld and Warhammer 40,000: Dawn of War) looks like it might just get me interested in WWII games- it looked incredible.
Worst things I saw at E3: The "Desperate Wives" game, a tedious Sims-like peice of suck... the arrogance of the Nintendo people- God only knows why people put up with those superior, smug buttwipes- you'e freaking GAME CODERS, not Jezus-fricking-CHRIST and His Deciples, guys, and I wish players would stop treating you like you are so your heads would shrink a little bit... Saints Row looked tedious as hell and murky to boot- I so can't wait until "Gangsta" games and "reality TV" are no longer popular... ... Also, they made an MMO out of the Pirates of the Carribean movie franchise... 'nuff said. Other than that, I saw a TON of stuff that was so raw and unfinished that it's impossible to make a judgement either way, but that's par for the course at E3.