The tech demos always look like they would make better game material than half the games that later come out.
This was THE issue with Aliens: Colonial Marines. The demo was outstanding and everyone thought that they were going to get that when the game was released. It never happened. The graphics were scaled down, the environments didn't look like the ones from the demo and the engine itself was buggy as hell. And of course they decided to make a DLC to fix some of these issues and to fill in some of the game's most jarring plot holes, but it never really did. While the internet is a good invention, it has sadly become the bane of modern gaming. Things that are left unfinished they fix after the initial release with DLC and m ost of the time it's just as bad and buggy too. There should be a law to state that any game which is incomplete in any way will not leave development.