IIRC, there were a few WW1 air combat games, although those are all fairly old games, and there is a
WW1 naval game out there, but other than flight simulators or naval games, WW1 isn't that great of videogame fodder for the same reasons Hollywood hasn't shown more interest in it. After all, trench warfare would make for a rather boring and often frustrating first-person shooter, real-time-stratgey game, or a more wargame.
I thoroughly disagree with the idea that WWI would make for a boring game. Video games don't need to demonstrate the first 24 hours of the Somme Offensive from the perspective of Private Jones, whose entire battalion was shot to pieces by a trio of German HMGs, to provide a compelling gaming experience.
Take this as a counter-example:
1st level: house-to-house fighting in a town or village in Belgium or northern France. Simple introduction, limited weapons (pistol, rifle, HMG, bayonet). Supporting artillery fire is coming from friendly and enemy artillery. Either way, it's blowing the hell out of the town. Can you throw the enemy out?
2nd level: standard capture the hill stuff. More weapons, more troop types.
3rd level: trenches - at night. Yet more weapons, more troop types, maybe body armour.
4th level: it's a videogame, so we don't need to stay in the same geographic locale. How about the Eastern Front? Or perhaps the Middle East? Who wants tanks? Light tanks? An armoured car? Flamethrowers? Maybe an incredibly difficult naval assault on a hardened enemy base? Who fancies an attack by Japanese troops against Germans in Tsingtao? &c, &c for future levels.
Tbh, I am useless as hell at all these FPS games (except Goldeneye and its successor), so I don't play 'em. But I do watch other people play 'em, and WWI has a variety of theatres and weapon types* that renders it suitable for videogame play. The real problem for such games is that it isn't
seen as a suitable arena, not that there is no way to make the game work. Trenches don't even need to be a major feature of such a game, tbh.
* Pistol, rifle, bayonet, shotgun, hand grenade, rifle grenade, light machine gun, sub-machine gun, heavy machine gun, flamethrower, and (effects felt onscreen, but used offscreen - usually) artillery shells and poison gas.