As far as I know, games set during WWII exist in every genre except sports (obviously) and JRPGs (there are some Western RPGs like Silent Storm).
My personal number one is Company of Heroes (Real-time strategy). According to Steam I've sunk over 300 hours in that game.
My personal number one is Company of Heroes (Real-time strategy). According to Steam I've sunk over 300 hours in that game.