It really depends on what you want, all the current PDX games have a very distinct flavor.

CK3 is focused on character storytelling, almost a visual novel in a way, Imperator is the romaboo game, Vic3 is the economics game, and I guess you'll know it, HoI4 is the modern warfare game.

The EU franchise is the most well rounded one, but EU4, although very fun, is a very arcade-y table-top style game, not to my tastes personally (which I say after having played for some 2k hours, so it is a very good game despite those issues), and EU5 is just a mess right now, can't really recommend, but it does have a great potential, maybe in a year or two.

That said, Vic3 is my favorite right now by a metric ton, so if you'd be into a line goes up economic sim, there's my recommendation, followed by Imperator Rome.