There are royalty free browser games out there. If one of the components allows displaying a website you can just make that page in the app be directed to the game and have it displayed in the app.
Yes, I know how to do it using “Custom Code” or with Iframe.
But it works mostly for HTML5 games and browser games.
There are templates for quality unity games that are usually the most popular games in the app stores.
I think in order to be able to use games like these a dedicated module is needed.
There is an option to export the game directly to APK or iOS and send to stores directly without “App Builder”,
But I think there will be a cool module that will support this because that way it will be possible to create more specialized apps in a more convenient way.
I think that might be out of the scope to add ios or android games to the apps. Unity uses C# for most of the programming language. NWICode does not use this language. You can though embed unity games into websites and use the previously mentioned method. I did not see any solutions on the web where someone has successfully combined a unity game into a ionic app.