Over the last few years I've played several titles from Total War, including Medieval: Total War (MTW), Rome: Total War (RTW) and their sequels.
The good things about these games are that:
1) Tactical battles. The 'units' are generally made of about 60-100 soldiers, organized by function in battle. Archers, close melee infantry, knights, and spearmen. Battle becomes in part a strategy session that involves trying to to make advantageous attacks, for example, getting your knights at their archers and melee infantry, your spearmen at their knights, and your archers good firing angles without them being in danger. It's a lot more complex, than that, but that's the basics.
2) Life has value. The characters left from a unit that takes many losses, or has been flanked, or takes a number of losses suddenly, may route. This is realistic. Many traditional warfare games involve creating troops in buildings, sending them out to fight and die, and then creating more troops, until one or the other side is overwhelmed. In Total War, soldiers fight as units for the most part, but also have that human element that has the characters trying to save their own lives, sometimes to the detriment of the human player that usually controls them.
3) I like the strategic struggle involved in the campaign maps. You fight for territories, similarly to other games. The people in a territory may rise up against the territory's ruler.
4) If you watch the History Channel, there's quite a few programs where they review medieval battles, and they use the Total War engine to create a computer generated picture of what the battle would have been like visually. It lets you see terrain, positioning, weather, numbers, types, and appearances of units of troops, etc. Very useful from an educational perspective.
I have a few reservations about the total war series as well.
1) While I like the historical information about inventions and historical events that come up, and I really like the period quotes from actual historical figures, I think the game introduces some limitations based on history that are illogical. For example, if you take over a territory that has elephants, but aren't from a faction that can create elephant units, then you can't create elephant units. Period. Yes it's true that the faction historically never deployed elephants in battle... but really the game is breaking from history with the first year when a human player takes over. Territories begin to fall, and history has changed. I think they should allow factions to adapt to the new history being made (the game does allow this to some extent) and allow factions to adopt units from territories they've conquered.
2) I would love to get away from the historical reality, and allow for some historical myths to play a part in the game. I would love some magic, or some mythical beasties, to play a role. It would really attract a larger audience. Historical peoples believed in mythical races, gods, magical powers, etc.
3) It would be nice if you could alter the territory lines by creating or destroying settlements. You could have territory lines expand by the size of a principal city, and when they abut with others, there may be some pressure to fight for resources.
4) My last big criticism of Total War games is the lack of an avatar like character. Obviously, when you're working with a historical faction over the course of hundreds of years, having a single character that will live that long is not going to be historical. And part of me is ok with this, because when a player invests too much in a single character, that character gets to the point where they could kill a couple of hundred normal people without batting an eyelash... and that's not very realistic either.
Anyway, Total War is still cool. I haven't played the new Shogun Total War 3 game (or any of the Shogun games) and maybe a couple of these issues have been addressed. Somehow I doubt it though. But anyway, if you look at the pictures I've added, you'll notice that several of them are from mods (where the standard game is altered) that put the Total War engine to work in Middle Earth, or with the Amazons, etc. I'm not a fan of making money just to make money, but I think the Total War people could make a fortune creating a fantastical Total War line of games.