Supreme Ruler 2020 Gold
A detailed RTS/Military Sim with LOTS of Replay!
I'm not sure whether to call Supreme Ruler an RTS or a wargame or some sort of political/economic sim, because it has a bit of all of those in it. You are the head of government and get to control policies such as trade, diplomacy, taxes, and such, but you can also become "Command in Chief" and take control of your army on a Battalion-scale. Anything you don't want to do (including control units) can be handed off to AI or "minister" control. There is a huge amount of depth in this game. The 'Campaign' game involves taking control of a single country (nearly any one in the world, from Congo to USA), and trying to take over the world. This has a lot of replay value. There are also shorter missions and scenarios that can be very military-oriented or in some cases a bit more peaceful. The military model is the most detailed I have seen in any strategy game - hundreds of modern equipment units to choose from to build an army, including trade and research of new designs, and a very realistic battle system. There are no limits in this game - you can literally build thousands of units if you want to, but maybe going for quality over quantity may be a better choice in the long run.