Hey Matthew! That sounds like a super interesting question.
I have found that there is quite a lot of similarities between gamers and athletes, so I would suggest to look at literature about coaching, athlete performance etc. Just from glancing over the resources, it seems to be a very complex topic and many seem to refer to "what are the variables you are looking for exactly?" since performance is a complex matter of (physiology, biomechanics, fitness in athletes), tactics and psychology plus situational characteristics. I guess the same, or something similar, goes for "gaming experience".
I think that gaming experience indicators can be:
-hours spent in game(s)
-achievements in games (performance, completeness)
-divergency in games played
-highest level of performance/ progress/ ranking
-active in community (often experience comes from reflection of others, discussion with others or developing addons etc for games, since you have to dive deeper into the mechanics of said games)
-(documented and published) tutorial writing
-coaching of others (helping in-game, on twitter, on twitch, in community)
-eventually: systems played on
-history of games/how long is said gamer playing games
- eventually: which status did they have in a guild (my guild liked to recruit people with "higher experience" like raid lead or class lead, since those people tend to be able to reflect and actively participate in planning [Gamereference here is World of Warcraft])
-can people adapt tactics (deeper understanding between player skill level, classes/champions (etc) played, team play, opponents team play...)
-how articulate are gamers about the game: can they cast? do they understand situations quickly and are able to instantly explain what is happening to others?
Okay that's what I had in the top of my head. Let me know if that was helpful - I'm very interested in that matter.
I recently came across a reference to the Game Engagement Questionnaire (GEM) of Taylor, Singer, and Jerome (2009) ("Development and Evaluation of the Game-Based Performance Assessment Battery (GamePAB) and Game Experience Measure (GEM)"):
A version of the questionnaire---tailored specifically for experience with first-person shooter games---is reproduced in Appendix A of Training Capabilities of Wearable and Desktop Simulator Interfaces by Taylor and Barnett (2011):
https://apps.dtic.mil/docs/citations/ADA552441
It seems reasonably well thought out, but by its nature, it certainly needs to be updated before being used; several questions refer to popular video games from the time of publication and first use.
Hey Matthew! Depends on your goal, for instance, if you want to know it since experienced gamers tend to be more prone to feel presence you have the immersive tendency questionnaire originally from Witmer and Singer and subsequent revisions by other authors more recently.
Not sure if you'll read this - but thank you for your responses! I'm going to explore all of them and see what fits best. Thank you again for taking the time to reply.