In order to generate reports on Gamification you need to go to Reports>User Reports and click on the User. On the right side, click on the green tab of Gamification (2), where you can view the status of Gamification for the User.
In order to view the overall ranking of your users, you can click on any feature, e.g. points (3), to check how the leaderboard is formed based on your user's progress. The same applies for the level ranking and badges collection.
Please note that the Administrator can view the leaderboard even if he switches to Learner mode by clicking on the green button with the points displayed, next to his name (4).
If you want to see the points, levels and badges of all your users, please export the system report and click on the user tab to retrieve this information.