When it comes to classic RTS games, Age Of Empires II is still a hallowed entry well worth replaying. Add in Steam Workshop content though, and you might never try a modern strategy title ever again.
One of the best is the Diplomacy Overhaul mod, which drastically changes the direction of the game, shifting away from combat into politicking and backstabbing in true GoT style. Be sure to play this one on multiplayer, though, as the game's base AI doesn't handle the changes well.
If you prefer something more along the lines of the classic Age Of Empires II experience, go with the War Of The Five Kings mod or the Game Of Thrones Map mod instead.