Vicky2 because of the economy and Pops. It's the closest thing we've had to a real supply and demand curve (EU4 has none), and there are a lot more options of amassing influence than direct conquest. Sphering countries for monopoly of a good was just as effective as controlling that province yourself.
I know it's rather ahistorical and harder to manage, but all the other games need Pop mechanics. Having a larger army meant having more soldier pops, which meant less people working your fields and factories. Then you enlist your reserves, and you go into debt because now nobody is working so you can't collect taxes. And when you lost people in war, that took a direct toll on your entire country. Imagine if that was how CK2 was modeled... it would really put a soft-cap on warfare. Enlisting 100% of your peasants would mean having nobody working the fields, and drive your cost up while having no income. Would really show you why fighting wars was hard.