In the days of unrealistic, quick, flashy real-time strategy, the Total War series stands out as the only of it's kind.
Aside from the excellent, large scale battles (which can be randomized, custom, or historical), there is a Campaign map, which blends together turn-based-strategy with real-time-strategy. Personally, I think the campaign map -makes- the game what it is.
Whether you're doing custom battles, or the campaign, you're going to have to choose what you want in your army. Basically, there's infantry, cavalry, missile infantry, missile cavalry, and siege weapons. There are many different types of these units, some better than others (ie, town militia are no match for armoured swordsmen, although both are considered infantry). You also get to choose, while deploying your troops, which formations to use them in, or to create your own formation.
The actual battle controls are easy to use, though it may take some time to perfect your usage of them.
The best thing about this game, for me, is that you can employ -actual- strategy, and have it work. Sun Tzu would be proud of this game.
If you're looking for a new game to play, and you enjoy strategy, you'd be advised to pick this game up - it doesn't cost much, anymore, either.