For all the complaints we hear of video game commercials that only show cinema rather than gameplay, we nevertheless are at a high point in how video game commercials should be advertised.
Microsoft led the charge with the now-famous "Mad World" commercial for Gears of War, which was a jolt to traditional advertising for video games. Rather than show various clips of gameplay, the short featured a cinematic with legitimate music specifically chosen to complement the visuals.
This trailer, as did many CG-driven commercials, earned the ire of gamers that it was all smoke and mirrors and no gameplay. However, this is different than the Medal of Honor commercials from years ago that tried to explicitly blend a first-person view with a CG trailer. I believe our current generation of "hardcore" gamers (that is to say, 18-30) are wizened enough at this point to ascertain what is actual gameplay and what is not; and I think this new-age style of video game commercials is cashing in on that knowledge.
I also believe that this new style of game advertising is truly a step towards the "games as art" movement, because of the beautiful level of (simple) artistry in these commercials. I don't think that these commercials are an attempt by the publishers to fool the populace into thinking the smoke and mirrors are the actual product; but I instead think that these well-made shorts are simply to raise awareness for their product. We live in the Information Age--any bit of knowledge on any subject you can think of is only a few mouse clicks away. All a publisher has to do nowadays to attract attention to their product is to make something that... wait for it... catches your attention. And what better way to get someone's attention by impressing them with a succinct commercial that blends compelling cinema with evocative music? This is why these shorts are called "teasers," as they are brief enough so as not to bore the audience, but interesting enough to catch their attention. They're perfect marketing.
Of course, there are some publishers who opt to go for the showcase of actual gameplay; but the ones who succeed at this method still understand that you need something interesting to complement the gameplay, because sometimes gameplay is just boring when taking out of context.
And of course, Ubisoft went this route (with great success, I might add) with the first Assassin's Creed, which kept the commercial in the in-game engine, but chose gameplay imagery which showed the emphasis of the game (parkour and assassination).
But regardless of the style, I think one would have to be mad to deny that the video games industry understands what it means to give a video game truly good advertising.
It's good to know that amongst the giant fuck-up that has been the HD Generation, the industry can actually do something right.