I approach engine tech demos with caution, as if they were primed to explode, or at least deceive me with their promises and lies. They're not necessarily representative of anything that will actually be seen in a game, unless you're one of those people who reckons iD games are tech demos, in which case they're the most reliably accurate tech demos of all. The new video advertising CryEngine 3 is utterly gorgeous, with lots of flashy pop-up text describing what's onscreen, whether its 'vegetation simulation' or 'tessellated toad tech', but take the embellishments away and there's still something impressive and that's the world of Crysis 3. Recognisable urban ruins being swallowed by the return of greenery, and water freed from pipes and cisterns. It's splendid and makes me want to do more in these surroundings than shoot people.
I actually feel a little bit disappointed when the soldiers and suit appear, but I don't suppose a first person post-urban exploration and wildlife documentary creation simulation would sell quite as well as a futureman biff and blast 'em up.