Only yesterday I was complaining about the rather poor mouse emulation and gestures offered by Windows 8.
For a Windows 8 touchscreen, it seems a middle mouse button (MMB) click has a much more elegant solution: TouchMousePointer.
This adds a new button to the taskbar that allows for a whole host of new mouse-like functionality for your touchscreen:
1) You can create an onscreen touchpad or turn the WHOLE screen into a touchpad (this is very useful for applications/games that are not optimized for touch, for which the precision of a mouse is necessary.
2) You can use the screen similar to a normal touchscreen*, but a click is only initiated when you put a second finger down (to the left for a left click, to the right for a right click, or 3 fingers for a middle click; this does mean you'll be using your middle finger for operating the device, but its not a huge change)
I had a play with option (1) above, along with StrokesPlus to try and make some action games like Skyrim playable (I did have better things to do.. But damn it). It kind of worked: A three finger swipe up to start walking forwards, a swipe back to start walking backwards etc. Using the screen as a touchpad instead of a touchscreen certainly made navigation much easier, however frankly having to use a gesture to move around feels pretty clunky compared to on screen controls. That said, there is a program called VirtualPad by PalmTime, which might make things much easier.
I've spent far too much time on this... In part a tribute to how poorly the interface is implemented in Windows 8**, and in part to the fact probably noone imagined these kinds of games would be used on a touchscreen.
*Presently, the author appears to be calling this "relative" mode, whereas it should probably be "absolute" mode since the mouse moves relative to the absolute position of your finger, not itself... But English aside, everything is very nicely implemented.
** At least as far as MMB is concerned, I mean how hard can it be? My touchscreen allows 5-point touch, and yet Windows doesn't actually utilise that ability.