I've posted this elsewhere, but it is still true three months later...
I would have to divide my Paradox experience into the "classic age" of (largely) pre-Steam CDs/DVDs bought from a shop (we were a simple people!) and the "modern age" stuff based around Steam.
Classic Age (starting from the best)
1. EU2; cracking soundtrack (I curse losing the disc for that reason), fun map, easy gameplay. A gem - who among us hasn't sent an army storming ashore with Vivaldi?
2. HOI2(DD); a very close second - it spawned an AAR (my one and only) that lasted for two years, and provided many happy hours of gameplay. Decent graphics, accessible gameplay, soundtrack ok (not as good as HOI1 actually) and happily, beautifully, moddable/editable.
3. Vic1; I have to confess that I dipped in and out of it - the countries felt a bit 'one size fits all', in that everything felt bent towards the economics of the game engine. The scale of the map though, was something to behold. And exploration/colonisation felt genuine. Compared to what came next, boy oh boy it was good. Worth it for the incredulity experienced when a uni friend was convinced that he had received a message saying "the HMS Cretinous is ready for deployment".
4. CK1; I have it, I vaguely remember it, but I think it's a bit of a "near miss" for me. It's just, well, a bit 'meh'.
Modern Age (starting from the best)
1. CK2; I am genuinely surprised that I have typed this, but amidst an abundance of riches, it is the standout. Lovely map, acres of playability, tons of fun to be had from mad/lecherous/zealous characters. I view it as a credit to Paradox that I haven't even touched (yet) the China or India updates.
2. HOI3; this is the 'slow burner' for me. I hated it when it was released, but with some well-judged updates/DLC it is a genuinely good game. It is the well worn pair of slippers that I keep for comfort. I have a slow running game that I have been playing on and off since Nov 18, and, as I know the game processes well, I can leave it for weeks on end and quickly reacquaint with.
3. EU4; I so rarely play it now, but was obsessed with it when it came out - one of my rare pre-order purchases, in fact. There is a lot to love - a decent map, some great ideas (the advisors in particular) and some good DLC. There are some minor things that are just ill-judged (ship upgrades - sorry, I'm not sold), and rebels seemed ludicrously overpowered, but it's a fitting update to a flagship Paradox product.
4. HOI4; that this game is 'mid table' is probably right - it could genuinely storm up to rival CK2, or with one DLC could sink into Vic2 territory. What works? The mechanics of industrial production are magnificent, for the first time in a HOI game warship customisation feels like a genuine exercise in "what capabilities shall I focus on", the division designer is very good, and I like concept of 'political power'. But... there is a place in hell for its approach to land combat, focus trees need a tweak, and its perception of C2 is arcadey in the extreme. Montgomery and Alanbrooke were not, on any planet, Field Marshals (or, in the abstract, Army/Army Group commanders) in 1936. It's just flakey. Grrrrrrrr…
5. Stellaris; is probably heading in the direction of CK1 above - 'meh'. I have only really enjoyed it with a pretty comprehensive mod installed, and have completely lost track of the DLCs. A solid game, but one that could have been great.
6. EU3; seemed to emerge for a couple of years and then got superseded by its little brother EU4. I know that its 'place in the sun' was something like five/six years, but by the time I'd given up on EU2, EU4 was in development. But, while it was "top dog", it felt like a logical development of EU2; I remember loving the map when it came out.
7. March of the Eagles; argh. The Napoleonic Era is, if I am honest, so dear to my heart (I'm an English kid who was a teenager in the mid-late nineties - it was Sharpe and Hornblower all the way) that I was pretty dismayed when this erupted and was then so poor. This is a period that deserves some attention - it is like the Cold War in that it doesn't really fit into the game that covers the period/adjacent period (EU for Napoleonics, HOI for the Cold War). It could have been wonderful, but it was tightly drafted, poorly executed and lacked any sense of the period in which it was centred. I type this yearning for a Paradox Napoleonic game that is any good. I'd sell the wife/house/car.
8. Vic2; take a reasonable game, remove some basic features (naming ships, FFS) that should, nay must be in the core purchase version, and make a global canvas seem small. How on Earth the colonisation feature could seem so awful is breathtaking. I genuinely cannot get into this, and my God I have tried. It is like Hollywood's obsession with Marvel films - "great, I am pleased for you that someone paid to experience it, but it is just never going to work for me".
Most of the above was typed three months ago - but, reading the hierarchy again, I do not alter it. I have yet to try Imperator, and given the reports on this forum I'm wary of it atm.