No other game comes close to having the number of unique armies which can battle in a real time environment. There are to date 15 unique army lists, and a lot of sub-factions function very differently from the more mainstay versions.
As someone who grew up loving strategy games where it wasn't a 1:1 matchup of troops this was everything I hoped for in a strategy game.
Much as all of the above is true, unfortunately the company doesn't prioritize bug fixing in a way I would say is logical or effective. It should be noted CA is infamous for abandoning a game the moment they stop producing DLC for it. As a result there is a bug which seemingly will never be fixed - if you have access to ambush (type of battle) attacks on your turn, the computer AI is disabled an won't mount any sort of tactics beyond the individual units reacting to being attacked. This wouldn't be as glaring to me if not for introducing the bug in the final patch. The modding scene for each Total War game is absolutely necessary to getting your full satisfaction of the product.
Thanks to all of the above this has become my most played game in my life, and with game 3 around the corner I doubt that will change anytime soon.