Gabe Newell's problem with Windows 8 and its Metro store are twofold.
First, it directly competes with Steam.
Second, it comes bundled with Windows.
Competition for Steam is good, but only if all of the stores are on a level playing field. This should mean that the Metro Store is an add-on that can be installed after the computer has Windows 8 installed.
This is Netscape vs. Internet Explorer all over again.
Netscape was the most popular browser, then Microsoft came along and bundled Internet Explorer with Windows.
Netscape is no more, and Microsoft lost an anti-trust case.
Some people will compare the Windows 8 Metro Store to the Linux Software repositories. But there is a key difference: You can add different Software repositories if what you want isn't in the default repository. Think you can do this with the Metro Store? Think again.
Yet other people will compare the Windows 8 Metro Store with the Apple App Store. This is closer, but Apple doesn't have the advantage of having ONE runtime for x86 and ARM platforms. Microsoft does. This effectively unifies the platforms and means that Microsoft will eventually extend into ARM and dominate it, since everything is written for Windows, not Mac or Linux.
The only way out is to either improve WINE drastically or improve ReactOS to the same extent. This will not happen without significant corporate involvement, such as Google contributing massive sums of money to either project (which does happen with WINE -- Google Summer of Code).