Today is officially a day of News and Revelations - more News and Revelations than it's possible to eat. Mere days after the discovery of a prototype animation reel for Obsidian's Aliens: Crucible, what appears to be a full 13 minute gameplay video of the cancelled title has surfaced on Unseen64 (thanks to AVP Galaxy for the tip-off).
It's a few years old and is work-in-progress footage, so the polish isn't quite there, but it should give you some sense of what the project might have come to, given a more willing publisher than Sega. In brief: this looks like Mass Effect with Aliens. Not quite the suspenseful return-to-roots I expect from Creative Assembly's secret next gen Alien(s) game, but not too shabby nonetheless.
Concept artworks for Crucible leaked in September 2011. They're worth another look.