I was always a GDW homer myself
Third World War series, Assault series and Combined Arms miniatures rules.
I'm also a shill for the computer game
The Operational Art of War III.
It covers WWI to Modern Period. Most of the scenarios are for WWII but there are a fair amount of WWIII scenarios. A lot of user created scenarios as well, someone made a good approximation of the GDW Third World War series for The Operational Art of War III.