The VGX trailer is just that, a trailer that was released 17 months before the game will be released. Games change. Trailers reflect the best foot forward of the game at the time the trailer is released. A "trailer" as defined in this context is:
a selected group of scenes that are shown to advertise a *[video game]*.
Advertise is defined as:
to call public attention to especially by emphasizing desirable qualities so as to arouse a desire to buy or patronize.
So in the context of a trailer, it makes sense that they would show you very good footage under very good circumstances to arouse a desire to buy the game. That's what advertising is. Taking a still shot of a youtube video and saying "it looks worse in this instance therefore they are liars" is disingenuous. Maybe there is no smoke because NPCs only light fires at certain times of the day. Maybe differences in weather effect the image. Maybe the systems are set to different graphics settings. Maybe there are compression issues. We just don't know yet. A lot of people are jumping to conclusions with limited and imperfect information. Patience is a virtue.
http://gearnuke.com/witcher-3-wild-h...er-comparison/ I think this article largely has it right in it's conclusion.
The most noticeable difference is of course the lighting in each of the scenes. While the general graphics remain the same, the lighting has been changed, probably to meet the art direction of te game. It could have been different to show a better view in the trailers compared to the final build. There are also some slight tweaks including different characters and armor.
What’s obvious from the above comparison is that the game retains its look very well from all of the pre-release footage.
There ARE some differences in the game from the trailer to the videos we have seen. Some (including myself) could conclude that the trailers look slightly better. There are three reasons that is not really that big of a deal.
(1) I would argue that one should have a healthy amount of skepticism whenever watching a trailer because it is advertising, regardless of who it is coming from. They are trying to sell something, and that is okay because otherwise they won't be able to make the next game. I don't know about you, but I really want to play CP 2077 and TW4: Ciri's Revenge. You cannot reasonably expect the game to look the exact same all the time from one video or image to the next.
(2) The trailers are a fair representation of what the game has become in my opinion. Even if it looks "worse" it still looks freaking awesome. I don't know of an open world RPG that looks better. How can being the best at what you are trying to be still be considered bad?
(3) We have all seen the videos showing the game as it appears now. So you cannot say you do not know what you are going to get.
*The actual merriam-webster definition says "movie" specifically. I changed the definition to reflect the context of our conversation.