Yep, I thought on creating a nice demo game, too. I am currently fleshing out a story for it, for I think a demo project without a plot is quite boring, while a demo with a reason to play through will be played through more often.
I'm currently creating the story in celtx, and as soon as it is usable, and as soon as I got a cool name for the project, I will talk to Mnenomic to get a subforum for the project and make the celtx project available to everyone who wants to contribute.
I am "everything but an artist", so I would definitely need help on this. I can provide scripting, sound, photoshop magic, plot, QA -- but in no way I can provide any artwork to use the magic on ;-(
The features to be displayed should also include the real basics, as well as voiceover, GUI Components, Inventory system, different interfaces, at least one first person scene etc.
And ... high resolution, high color, detailed animation and high end production -- I wont to have this demo look "as commercial as possible".
In my first designs, I thought of NOT using a 3D charakter, for if the backgrounds are done in Photoshop, creating the hidden geometry might be a hard task. BUT: If someone can do this, it would be great. If we use a main actor as 3D Actor, we could use 2D NSC to show it's possible as well ;-)