This rating system means that everybody who is allowed to upload directly and edit, can setup and modify the rating system. The rating does not change the quality of the asset, but adds an extra dimension to your search.
Go to Settings > Taxonomy > Metaproperties management and create a new metaproperty called Rating.
Choose Select from the Type drop-down.
Select the following features of the metaproperty:
Empty options in filter
Show in grid view
Click + Add Options.
Enter the name and the label for the rating. See the image below for an example:
Save the options and save the metaproperty.
Go to the assets overview and click on an individual asset. Open the Edit tab. Alternatively, in the assets overview select multiple assets to edit them.
Open the Rating tab and select the desired rating.
When you save the assets, the rating will be added to the Optional fields. It will also display as a filter. See the image below for an example.