You can supply ratings for the following content types:
Google also supports reviews for the following schema.org types:
[CreativeWorkSeason](https://schema.org/CreativeWorkSeason)[CreativeWorkSeries](https://schema.org/CreativeWorkSeries)[Episode](https://schema.org/Episode)[Game](https://schema.org/Game)[MediaObject](https://schema.org/MediaObject)[MusicPlaylist](https://schema.org/MusicPlaylist)[MusicRecording](https://schema.org/MusicRecording)[Organization](https://schema.org/Organization)
Check the definition of Game, I think in your case it should be a Organization type.
Original post credit: https://support.google.com/webmasters/thread/14697981?hl=en
