The Crusader Kings series focuses primarily on individuals, their traits, their dynasty, managing your court and vassals, rather than focusing on nations. This

The Crusader Kings series focuses primarily on individuals, their traits, their dynasty, managing your court and vassals, rather than focusing on nations. This means that the game is less of a grand strategy title, and more of a role-playing game. At it's core, you scheme, you wage war and you play the diplomacy game by marrying and allying. I just had a playthrough in CK2 AGOT (A Song of Ice and Fire mod), where I role-played as a lunatic obsessed with religion, burning people, sleeping with other people's wives and having incest relations to expand my bloodline while keeping it pure. Vanilla CK2 (and CK3) are all about this moment to moment character driven gameplay. EU doesn't really focus on the individuals as much, and it's more of a traditional RTS game if you will, with resource managing as its core, rather than character roleplay. EDIT: Should probably mention that the time period is also very different, but mechanically, they're different games. Same with Hearts of Iron or Victoria. They all look somewhat similar, but they all have their own quirks that set them apart from each other in terms of gameplay.