Everything.

The powers. I want to possess people, teleport, stop time, etc. I never get cool powers in a first person game; the closest I got too some was Crysis 2, but that game was artistically boring, the character was boring and silent, and the powers weren't even amazing or crazy.
The setting is another huge factor.

You need to try Bioshock.

and bioshock 2
and bioshock 3

I can't pick a favorite for a number of reasons. 1: I like gadgets, magic and so on the same. 2: From what we know and have seen so far they seem to very well balanced. Although I fear that some powers or stats will provoke players in playing a cookie cutter build. In Deus Ex everything was balanced except for Poison Resistance, Swimming and the Tranquil Darts. So I fear that some powers or gadgets may be a let down. For example Feather(no fall damage) doesn't sound very useful. And they also mentioned that Possession kills the inercia while falling. They need to talk more to the testers and see if there are no cookie cutter builds or ways of playing in general.

I don't want it to be Deus Ex: Human Revolution, where hacking can get you everything in the game and is considered the best playthrough. And ofc my biggest concern is if the stealth system is refined. Looking at the team it seems like it's going to be, but I can't be certain just yet. Also I really really really like the mask.

The ability to tackle missions on different ways. Also, the ability to posses other lifeforms really opens things up.

Its not free roam. Sorry to break your heart.

Either way the setting is the primary reason I am excited for this game. I like dragons and beasts and mythological creatures but that setting has been shoved down our throat for years. From what we have saw the city looks amazing.

because skyrim or other TES wants to be the "do all" and "be all". so i guess they couldnt focused on every single intricate detail.

Just that a developer these days has the balls to dare the player to forge his or her own path as they see fit. Too many recent campaigns insist on holding your hand and spoon feeding you the whole way through.... succumbing to the casual majority to make a buck.

I'm just looking forward to a single player only game (that doesn't rely on the devil's internet) that feels like a fresh, different experience every time I play. I'm all about immersion, high replay value and a break from the tedious high maintenance pressures of competing in online shooters. Enough foreplay, I wanna make love to this game already!!

And I'm going to try my damnedest to stay away from those youtube videos for as long as I can because I want the satisfaction of exploring and discovering those creative methods by myself.

Don't stay away. I watched a video for dark messiah yesterday that showed me somehting I've never even thought of in my 6 total playthroughs.

With Bioshock delayed, this is hands down my most anticipated game. Even when I thought they were both being released this year, this game edged it out because of the greater sense of narrative choices I would make with my actions---I'm really looking forward to being the craftsman of my own tale, and my toolbox of supernatural abilities along with gadgets to do so sounds awesome. I can't single any one thing out. I'm going to say the music and sounds because I have no idea what those aspects will be. Q4 can't come soon enough.

Stealth and The Outsider!