Pheace: So, you think every developer will start making games with engines that can only be used in WinRT and thus only be sold through the Windows Store you mean?
Developers make games that people want to buy.
I think many end-users start expecting WinRT features from their new games, even if it means something mundane and simple like being able to navigate in the game menus with optional touch screen controls (ie. touching on "New Game" instead of clicking with the mouse on it). It seems to me that already now more and more x86 PCs, at least laptops, come with a touch screen by default, and I expect that in a few years PCs without touch screens are not necessarily even sold anymore.
I think this discussion is also a good example how users start expecting WinRT features from all the software they run in Windows 8:
http://www.gog.com/forum/general/windows_8_tile_icons_do_we_need_pin_gog_like_pin_steam I guess it is a bit similar phenomenom like "normal user does not accept games anymore which need to be installed manually, and where patches have to be installed separately too". I mean, a Win8 game without (optional) touch screen controls in the menus? That's almost as bad as a game without auto patching! What is this, 1999? :)
While MS-DOS games ran just fine in Win9x, people mostly just stopped buying more of them, and wanted to buy Win32 games instead for their Win9x boxes. I could easily see a similar thing starting to happen in the long run also with Win8, when enough people have migrated to it. I think Microsoft has already stopped delivering Win7 to OEM suppliers, so more and more people will migrate.
As for WinRT games not ever being up to par with legacy Win7 games... that Hydro Thunder game I loaded yesterday from the Windows Store seemed quite good with its detailed hires 3D graphics. I believe it is a WinRT based game? I think it looked just as good as legacy desktop racing games I've seen, I think it was even running in 1920x1080 resolution.