Those games are probably designed to run in full-screen mode. Many popular games utilize the DirectX™ technology to render 3D graphics. When these games are being played in full-screen mode (that is, not within a window), their graphics engine uses the DirectX technology to draw graphics directly onto the system's screen.
If you are trying to use Splashtop Remote iPad to play one of these games on a remote computer which is running in full screen, this situation will result in Splashtop Remote being unable to capture the desktop screen correctly through the Microsoft® Windows® screen-capture APIs. In this case, you would need to reconfigure these particular games to run in "windowed" mode; that is, to run within a window. Although Splashtop Remote does not currently support applications that require direct screen access, it is planned to have this capability in a future version.