First of all, I haven't played all games of the Total War franchise, only Medieval 2 and a bit of Rome 2, but Shogun 2 was the best so far. Its really captivating and its one of those games which can tie you to your chair for hours and hours, just like Anno 1503. I'm not bad at strategy games but I think that even for strategy newbies this game will be easily understandable and enjoyable.
-The setting. Feudal Japan is cool, Samurais are cool, Ninjas are cool, being Shogun is cool.
-The graphics. Ok, the map is not the eyecatcher here but the battles are. The details are amazing and you can follow each samurai until his death.
-Intuitive control and UI. Its impressive how easy to understand this game is. The principles and priorities are clear, you don't have to search for anything and the interfaces for diplomacy, trading and all that stuff are well done.
-Sound in general. Wether its the effects, the music or voices (the japanese accent sounds great), everything feels right.
-The campaign. Its pretty long and its full of surprises, you can always do something in a different way than you did before.
-The characters. I'm talking about the generals, daimyos, ninjas, metsukes and all these people. I got pretty attached to them and it was exciting to see how they grew with the time (plus the skilltrees are awesome).
-After you've finished the big campaign, there ain't much to do, you can go for the DLC's like Rise of the Samurai and Fall of the Samurai, but if you want to play the campaign again I noticed that you don't get any more clans that you can play, like in Medieval 2 for instance.
-Sometimes you have to repeat battles (if you mustn't lose them) and it can get pretty frustrating after the 17th try.
I highly recommend this game and if you enjoy feudal japan and strategy games, get this game. Now.