Wasgo: I'm certain based on the clues that it's Halo. The countdown is positioned to be replaced with the letters H, A, L and O. The words unexcelled can easily refer to something from Microsoft other than Excel and the graphic would work perfectly for Halo as well. In addition, it meets the criteria for a game that was previously mentioned.
While Halo might not be the most exciting game, if Microsoft is now supporting GOG.com it would be a huge coup, as it would be an amazing signal to other publishers than the GOG.com method should be supported.
Also, Microsoft is a top 3 video game publisher by revenue: [url=]http://kotaku.com/5030320/here-are-the-top-20-publishers-in-the-business-ranked-according-to-cash-money-intake[/url]. Not sure if that's accurate for PC games, but I'm certain that would still hold for gaming revenue.
I don't think Microsoft has any interest in supporting a small, DRM-free store. Not to mention that, besides Flight Simulator, they don't really have much in the way of "good old games".
That said, Bungie is independent these days, so Marathon would be far more likely than Halo. (If they even still own the rights.) But I'm sticking to my prediction that it will be a major deal with a publisher rather than a studio, and my bet is on EA.
In unrelated news: this thread is getting pretty insane. Are we talking about GOG or the Apple Tablet? The hype is out of control!