I'm a long-time fan of Paradox's games. Ever since I discovered Europa Univeralis (EU hereafter) 2 about 11- years ago, I've been obsessed. I've shoveled time into the likes of Victoria, Victoria 2, CK2, and EU3. So, as a long-time fan of Paradox, how do I feel about their new game?
Simply put, this game is great. It takes EU3 and improves upon it in every fashion. They streamlined almost everything (especially the UI) and made the strategic choices -much- more clear pretty much across the board.
Let me give you an example here. In previous EU games, diplomacy was easy to game. Give a country a lot of money when you need them; ignore them otherwise. Make alliances just before starting a war and avoid going to war for your allies. Then.. well.. re-ally with them once their war ends. Sure, they're a bit upset, but you can take care of that with a little bit of cash and a royal marriage.
EU4 changes all of this. You have a limit on the number of diplomatic relations you can have. You have a limit on the number of diplomats you have. You can only improve relations (no cash involved) up to a certain level. If you fail to show up for an ally's war, they -will- remember it for years. Do it twice, and you'll probably no longer be a serious choice as an ally anymore for said country. Simply put, you can't just do what you want with diplomacy anymore. They've clarified and reinforced the strategic element. You need to carefully consider your options and stick with your plans.
In a game as Ireland, for example, I fought dozens of wars for my ally France. I decided to skip out once, because of domestic issues, but I found France no longer willing to ally with me. I was then obliterated by the UK, which no longer had any worry about going after me. I reloaded and fought that hard war for France, but they stuck by me in recompense. These are hard choices, but they are important choices.
This approach colors the entire sequel. The monarch power system, which replaces the old sliders, tech, and ideas, is all about creating hard but important choices. Do I get that awesome military idea, or do I stay level with everyone else's tech? Do I expand my empire, or do I keep my administrative tech up to date? Do I build a bunch of tax/production buildings, or do I increase my stability? Again, EUIV highlights strategic choices above all else. The monarch power system is a harsh, unforgiving system, but it highlights the importance of the choices you make as a player.
The trade system is also entirely different than the trade system in EU3. I won't go into much detail here, but, suffice to say, it works very well. You actually feel like you're making a trade network, rather than just playing Center of Trade whack-a-mole. The new trade system depends strongly on sending fleets of light ships to "Protect Trade" in different trade nodes. This creates an interesting new dynamic, where you need light ships to sustain your trade network but heavy ships to protect your light ships in war. Managing the ratio here is another example of the strategic choices the game gives you. It also means that war can be disastrous for your income, as any unprotected light ship fleets may need to head into port. You can also embargo other countries in order to hurt their trade in nodes where you have the trade power to do so. However, doing so will create a casus belli as well as massive negative relations with said country. The result is that the trade system feels closely tied to the diplomatic elements of the game, highlighting the strategic importance of the decisions you make diplomatically and economically.
There are plenty of other differences as well. The AI is much better at fighting wars. Coring, diplo-annexation, religious conversion, and cultural conversion are all very different. They are tied more to other systems in the game and are much less dependent on chance. In every case, you actually have a progress meter, and you can tell, rather easily, what is impacting said progress in one way or the other. In EU3, by contrast, random numbers dictated most of these elements.
There are loads of other differences, but I won't go into every single one. I'm just trying to give a sense of how the game generally plays. The truth is that Paradox has really hit the ball out of the park here. The game feels much richer than EU3 ever did, and everything just slots together nicely. In some ways, EU3 felt almost too.. disconnected from its game mechanics. Many of the mechanics were relatively easy to maximize, and they didn't connect to each other in clear, important ways. EUIV has definitely placed game mechanics and interoperability to the front, which does a lot to make the game fun. It also does a much better job introducing and explaining itself, though a true noob will probably still want to check out some guides.
Are there problems with EUIV? Certainly. The game has a few technical issues (most of which I haven't seen myself but have seen evidence of), and the balance is a little off. Light ships are a bit overpowered as is, and, at times, it feels like the monarch points system is a bit too disconnected from the other mechanics. However, all in all, we have a great start to a great game. It's easily amongst the best games "at release" in Paradox's history (alongside CK2), and I highly recommend it for any fans of the series.