Samurai Warriors 2 + Strategy = Greatness
Samurai Warriors 2 improved on alot of what was missing in the first game. For one, you have many more unique characters to choose from. This provides variety in the gameplay. It also improved the "skill system" which is like Dynasty Warriors' items in that it gives you skill boosts and other nice effects. It works alot better than the item system does as the effects of the skills are permanent.
Now, all this sounds dandy, but the reason I'm giving this game such a good score is because Empires adds the element of strategy that makes the game even more fun to play than the original. The whole point of the gameplay is that you start out with a single piece of land and through diplomatic or violent means, you take over other peices of land. Depending on the scenario you choose, this could range from just a few warlords controlling all of the land to many different warlords controlling a single piece of land. The AI for these scenarios range from extremely aggressive (where they'll likely attack you alot) to extremely subdued (where they'll hardly ever attack you). When your land is under attack, you have the option of defending it manually or automatically. If you defend it manually, you'll do it through a battle. If you do it automatically, the computer determines the outcome of the battle for you. This is dangerous in that you might lose the land.
There is also a Create-a-Warrior option. The options for appearance isn't extensive as I would have liked, but you can choose self skills and move sets that will make your warrior unique.
All in all, if you are a fan of the Dynasty Warriors or Samurai Warriors series, you'll really enjoy this game. If you've never played any game in the series, I'd suggest you start with the regular Samurai Warriors 2 game and then play this. That way you'll be less confused to the background story of each character and stage.