It’s not the period what makes you like the game.
It is and it isnt.
For some people its all about immersion, the idea of the alien strogg race playing as a faction in the game breaks it.
Or to take a game based on WWII, a player might want to simulate or recreate the experiences in their mind, from the stories their grandfather told them when they were 5.
Then you have people that only care about gameplay.Playing a game based on the Vietnam War, might mean very campy gameplay, with a heavy focus on guerrilla warfare tactics. The games damage model might be so sensitive that it allows you to kill players with one bullet in the toe.
So a lot of it comes down to how much realism the dev wants to bring to the game, and whether the player likes that type of gameplay.
Then you have those in between. They are willing to play a game with say the strogg alien race as a faction because they value the game’s gameplay, but they will always play as GDF.