Two market forces are colliding. Media is converging to a single digital platform. We have online versions of a number of TV shows, copies of newspaper content, of magazines, etc. As online media gets richer (both literally and figuratively), there have been many questions raised about the right ad format. The second market force is casual gaming. By lowering the bar to step into the games, casual gaming has expanded the gaming audience to new demographics and wider numbers.
Eventually, the two are going to hit. As anyone who has played one of the highly successful "WarioWare" games from Nintendo knows, it takes but a few seconds to see a concept, understand the concept, and successfully interact with the concept. In Nintendo's games, it might be pulling nose hairs or cutting vegetables, but there is no reason that in less than 30 seconds one couldn't have a user drive through rocky terrain in a new model of SUV, or jump through an obstacle course in a brand's new basketball shoes.
Ads that have game elements are being attempted in banner ads (though these are not done particularly well, in most cases), but banner ads are not the right format for a short casual advergame. Interstitials are the best format for this. And in my opinion, it would be a far more successful format than repurposing 30-second spots or cutting them down to 15-second spots.
On video sites that have commercials, I keep a second window in my browser open, and when an ad comes on, I switch back to reading the article I have open until the ad finishes and my content comes back on. With a short advergame, a marketer can make engagement mandatory to continue to access content. The games themselves can and should be easy enough that a child -- or perhaps a better example, their parents -- could do it; additionally, an alert user should be able to complete them in less than 10 seconds. And perhaps most important, even in their short duration, they should be fun, and a win should be rewarded in some way.