I've added some more detailed impressions to the Op, as many people in this thread were prompting me for them:
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As people were asking for more detailed information, I'd like to add some additional impressions.
In general, the most obvious graphical flaw: Aliasing absolutely everywhere. Of the "graphical powerhouses", I noticed it the least in Ryse and FIFA (anything but impressive on any other front), most of everything else was marred by it (Forza certainly, BF4: OMG aliasing is everywhere!)
These were the games on display:
Battlefield 4 - was playable in a local multiplayer configuration (8 vs. 8 on a warehouse type conquest map with a bit of an outside area. The game seemed like a huge mess, extremely noticeable aliasing as well as huge amounts of pop in were maring the experience. The already mentioned leaning-interference by Kinect (which can probably be disabled) further soured me on this version of the game.
Crimson Dragon - didn't seem like my type of game, only played it for a short while
Dead Rising 3 - had a free-roam demo without any stated aim, I quickly tired of the gameplay (slaying hundreds of zombies, combining items). Graphics didn't impress either, but didn't notice any performance problems. Could display a huge amount of enemies present, although they never felt all that threatening. Driving over zombies in a car was fun for a short while
FIFA 14 - really hard to see what's "next gen" about this title, there's absolutely no reason to upgrade for this game. Could almost pass for an Xbox 360 or PS3 title, except for the higher resolution (that isn't really a huge factor to the overall impression)
Forza 5 - looked nice, even though I expected more out of it as a graphical showcase. It seemed less of a leap than I was hoping for. The impulse triggers (individual vibration for both triggers) were put to great use in this game, you can kind of "feel" the brakes, which is pretty cool.
Just Dance 2014 - didn't play, just watched - I think what you expect is what you get
Killer Instinct (with gamepads as well as fight sticks) - seemed fun, but I'm not really qualified to judge fighting games. Not something I would ever play were I to own an Xbox One.
LocoCycle - graphics are very plain, as is obvious from all the existing media on the game. In game talk (commentary by mechanic and main character hanging out of motorcycle) seemed rather annoying and unfunny. Gameplay was not complex from what I saw, shooting and beating cars, other cycles and flying enemies.
Ryse - reminded me of a prettier Uncharted in terms of graphics, suffered some small stutters that interrupted gameplay which was wave based arena combat ("horde mode") that got tiresome very quickly as combos are very repetitive and tasks (emptying cauldrons, defeating catapults) to complete among fighting enemy waves in the arena were repetitive in terms of required player action (walking/rolling over to direction marker and pressing a button).
Zoo Tycon - a limited management game, didn't seem to offer much creative freedom in terms of park layout. Certainly don't expect fine-tuning and building on the level of a Roller Coaster Tycoon. This title suffered extreme performance problem, and certainly didn't look pretty in return for stuttering.
Kinect Sports: Rivals - Very reminiscent of Kinect Adventures, gameplay seemed equally uninspired (leaning and opening/closing hands for jet skiing, and stretching and grabbing as well as jumping for climbing. Pretty graphics for games of this type.
Peggle 2 - it's Peggle!
Max: The Curse of Brotherhood - didn't play this one
That wasn't really my point though.
