You'd be surprised what LucasArts adventure games fans like -- there's a Mixnmojo Steam group where people regularly play TFT for example (http://steamcommunity.com/groups/mixnmojo
I've wondered about this as well. I think it would be possible to make a WW1 shooter, but harder. Most of the conflict was trench warfare which doesn't lend itself to a game (waiting for a few months in freezing and noisy conditions before being sent over the top and mowed down by a machine gun).
That said, there were areas where the conflict was different. Parts of Africa, for example -- though I don't know much about that.