[2] Crusader Kings II attracted a wider audience than Paradox's previous games, contributing to the growth of the company.

The game depicts or mentions numerous historical figures, including William the Conqueror, Charlemagne, Genghis Khan, Harold Godwinson, Robert Guiscard, Robert the Bruce, Harald Hardrada, El Cid, Constantine X Doukas, Harun al-Rashid, Alexios I Komnenos, Richard the Lionheart, Ivar the Boneless, Alfred the Great, Baldwin I of Jerusalem, Boleslaw the Bold and Saladin, but allows for the player to choose less-significant figures such as minor dukes and counts, and for the creation of entirely new characters with the use of the Ruler Designer DLC.

The game employs a genetics and education system, through which children inherit many traits, culture, religion and skills from their parents and guardians.

In addition, all non-Christian characters are unplayable without the purchase of the DLC that unlocks them, including Muslims, Jews, Hindus, Buddhists, Taoists, Zoroastrians, Jains, Zunists and various pagans.

[39] GameSpot reviewer Shaun McInnis stated: "Through a complex system of diplomacy and backstabbing, Crusader Kings II makes every power struggle an engrossing one" and he lauded the gameplay while noting the "lackluster tutorials".

[35] A reviewer for Rock, Paper, Shotgun wrote that Crusader Kings II was "probably the most human strategy game" he ever played.

[40] Rob Zacny of PC PowerPlay, who gave the game a 7/10 score, called it a "brilliant treatment of feudalism in terms of strategy and story" but also stated it "requires major investment to overcome information overload".