Here's a list of every game currently available in the xCloud program.
Currently in Preview, xCloud is Xbox's streaming service, allowing players to play games of all shapes and sizes directly on their mobile devices and other screens. It's only available on Android for now and uses a plastic bridge to connect an Xbox Wireless controller to your device. In the future more controllers, including the DualShock 4, will be supported by xCloud.
There is no word yet on if, when and how the xCloud games list will change. At the moment, anyone lucky enough to be in the Preview program can access all of these for free.