One might argue that Angry Birds could have done the trick for Microsoft if they had been able to act sooner, but, at this point, I think it's unlikely that a game can make it happen. Microsoft's best way to increase market share on Windows 8 is through business channels, not through consumer ones (too expensive; they've lost to Android and iOS already), and not through educational ones (too expensive; lost to Google at the moment).
I think Microsoft's best shot here is through Lync and Skype and building out the collaboration tools in Office (Word, Excel, Powerpoint, Outlook). Google Docs is simply not as good as Microsoft Office, except from a collaboration standpoint (but Office 365 is pretty darn close). These all have good network effects, and if business adoption is solid, I would expect that they'll make the jump from business to consumer, and also to education.
"Solitaire for Windows 8" implies that there hasn't been a paradigm shift, and that's wrong. When Windows 3.1 came out, most households didn't have a computer--or if they did, it was far inferior to what's at work. But today, most households have smartphones and tablets that they view as superior to the locked-down systems they use at work. New paradigm.