Setup 1 Google Analytics property code and then apply it to the sites you wish to track.
Then in the Google Analytics dashboard, navigate to Audience > Technology > Network, and then click on 'Hostname' (between the chart and the table) and you'll see a list of domains and session stats.
You can also use some of the main dashboard reports in there by also changing the primary dimension in them to 'Hostname' often using the 'other' dropdown (between the chart and the table) and then expanding 'Behavior'. An example of this would be the report found under Behavior > All Pages which you can use to get the total page views per hostname.