If it's about length, there is really nothing beating Pride of Nations. If you pick the 1850 scenario, you will have 1680 turns to play. That will keep you occupied for a very, very long time. PON however is not only a military game, but primarily about nation building - there will be wars along the road of course, but you will also spend a lot of time building up your nation. It is grand strategy in the truest sense of the word, as it offers you the entire globe.
Revolution under Siege is more comparable to CW2 in that it is primarily a military endeavor, but the scope is vast, as it depicts the entire Russian Civil War from European Russia till Vladivostok on the Pacific Coast. The grand campaign goes from 1917-21, and there are three sides to play, so there is definitely replay value if it is a military-oriented game on a large scale you are looking for.
And of course To End All Wars is coming out today.
