Facebook games in Safari
App Store rules make it impossible to offer cloud gaming services in the App Store and Facebook is now running into the same problem. The company would have liked to release its own app, but is now dependent on a (progressive) web app, which you can find here. From this week you can play the games. Microsoft previously ran into the same problem: Apple's App Store guidelines don't allow such apps unless each game is submitted for review separately. That's unattainable.
Facebook's vice president of gaming, Vivek Sharma, says that's why he's come to the same conclusion as the companies that came before him: bringing cloud games to iOS can only be done through a web app. Sharma also took the opportunity to criticize Apple for saying the guidelines “destroy the idea of cloud gaming.” Apple's hurdles prevent people from discovering fun games, playing cross-platform, or directly accessing high-quality games through a native app.
Incidentally, many Facebook games, such as Angry Birds and Asphalt, are also available as separate iOS apps. So you don't need Facebook for that.
Similar story at Microsoft
Microsoft made Xbox Cloud gaming available through Safari in June. This has the disadvantage that the web apps are limited in functionality, cannot send notifications to users and are more difficult to find. It is also less possible to take into account the specific hardware you have.