To understand if a game is working or maybe how you could improve, you need to collect feedback.
Feedback is one of the core attribute of the agile mindset and, for a game, comes mainly in two modes: from play-testers and from actual players.

To collect feedback of a game I have created a dedicated model called TARGET from the initial letters of the 6 dimensions:

• Theme: Is the theme enjoyable and close to reality? Are information on which game is based on realistic? Is the goal of the game consistent with the theme?
• Aesthetics: How is material in the game? How is the iconography of the artefacts? What about readability of the information (cards, rulebook,…)?
• Replay-ability: How your knowledge of the game can change the game experience? How many variants you can play? How many players combination?
• Game length: Is game length consistent with theme? Are there some moments where some player is only watching? Is the flow of the mechanic fluent or start&stop?
• Easy of play: Are rules clear and straightforward? Are there some weird exceptions to normal flow? Are there support to explain the game?
• Tactics & strategy: What is the role of luck? Can player predict, monitor and control different phases of the games? Are players able to adopt different working behaviours?

You can measure each of these with a score 1 to 5 (or stars) and with an open text to ask to the player how to improve the actual score.

As you can imagine this can be easily automated using an online form. FOR EXAMPLE at the following link you can find the google form I have created for Agile Game Factory’s customers.