You existing Entities may not help you very much here. So on your GameEdit page you need a Datasource microflow, which spits out the Non Persistent object which is associated to the actual Ratings Given by the Player(s) for this GAme, also at the same time show the Aggregation of the Ratings in that 5 * UI that you already showed above.
So put a dataview on the Game Edit page where the source is a Microflow. This microflow will receive the current Game object and will return 1 Non persistent entity that has the aggregated value as well as the association to all the ratings that this Game got.