Anyway, it should be obvious to most wargamers that there are different styles of play, ranging from pure game to pure simulation, and in theme ranging from pure fantasy to pure history.
Everyone should find a playing style he or the group he plays in (I use ‘he’, my apologies for the single female wargamer out there) are comfortable with. I don’t think there can be much discussion about that.
The interesting point to discuss though is whether one can claim a specific ruleset is able to recreate a historical event. With this I mean whether, within the model of the game rules, a scenario as it unfolds on the table could have been possible in reality. This is a valid question to ask, and is independent of the question whether one likes a game should be simple and fun, a simulation, or something completely abstract. It is even an independent question of what role the player is suppsoed to represent (Bn commander, Corps commander, …). Even if you move and act with every individual soldier in a divisional-sized game, the overall result could still be historical accurate.
The question whether the game as it unfolds on the table could have happened in reality, can by itself be considered from different angles:
Theme: it’s sort of obvious any non-historical setting (fantasy, scifi, …) fails the above test immediatly. The closest you can get is try to mimic events as described in books or movies — which is a valid starting point by itself, IMO. But theme is also whether unit/army X could have been facing unit/army Y. It’s obvious the Romans never fought the Aztecs, but the question can also be considered on a smaller scale: would it have been possible for a platoon of transmission troops to face a platoon of Tiger tanks? Did such an event happen? COuld it have happened, or was such an event very unlikely, given what we know about the real historic events.
Technology: Would it have been possible for weapon X to destroy device Y? (weapon or device can be troops as well). The typical question whether cavalry can ever break an infantry square belongs here.
Tactics: Would troops of type X have been able to perform the actions on the gaming table, given the tactical doctrines and possibilities of the period?
Time: Would it have been possible to perform the actions on the gaming table within the time frame modeled? Are movement distances/fire ranges/casualty rates in correct scale to each other?
Any of these aspects can be problems in their own right, and can be interesting discussion points.
In my opinion, the ‘historicity’ of a game is then a sliding scale, depending on how well each of the above aspects are present in the final game being played.