Oh boy, I hadn't seen this before. This is wonderful.

Paradox is known for making very complicated, somewhat buggy, but lofty and (in my opinion) very fun titles.

I swear their approach to games is "So they say 'a game is a series of interesting decisions,' lets see how many decisions we can pack into this one!"

The Hearts of Iron series is basically SimCity for World War 2. You pick any country and a starting year and just go. Decide on major events, pick your cabinet, how you allocate resources (industrial and brainpower), who you spy on, what you research, elections, and of course the whole war thing. Just everything. The game is huge fun if you like to sit down and plan things and I totally recommend it to anyone who loved the sim cities of old.

Hearts of Iron 3 is on Steam here: http://store.steampowered.com/app/25890/

This is a Paradox Interactive published game, not a game made by related Paradox Development Studio which makes HOI, Europa Universalis, etc.

There's no direct relation.

While Colossal Order is not a Paradox studio (besides Paradox Development Studio, they also have Paradox North, Paradox Arctic and Paradox South), it has very close ties to Paradox Interactive. Colossal Order was present at Paradox's Fan Gathering at Gamescon in Cologne this August for instance.

I hope it turns out better than the several versions of Cities XL did.

I don't think they are related, unless I'm missing something

Despite their titles, Cities XL (developed by French developer Monte Carlo) and Cities: Skylines (developed by Finnish developer Colossal Order) have no relation. Colossal Order have already stated that they will avoid some of the design decisions made by Cities XL (such as specifying where which class of people lives).