I never bought it because of it's reputation, but I have been hearing about how 2.0 is an amazing hidden gem. So what is so great about it compared to other Paradox games? (My favorite ones are Victoria 2 and (to a lesser extent) CK2, if that matters.)
I can only tell from what I personally enjoy the most, but the game has a lot more to offer than just the coming points.
Imperator has a deep combat system that is also well-understandable.
Pops simulate a population and a lot is based on them: research, the amount of troops at your disposition, tax income, goods produced for trade and local use.
There are 4 different rights a culture can have: Nobles, Citizen, Freemen and Slaves (there also are tribesmen pops, but they aren't a pop right); based on that the pops of the given culture will tend to promotoe (or demote) to that role. Nobles are research, citizen reseach and manpower, freemen are manpower and tax and slaves are pure tax. Besides for slaves, a pop's happiness will dictate its output.
I like the technology system. It works as follows: you have research produced by nobles and citizen. Depending on research ratio (based on integrated cultures), your technology has a different speed. There are 4 different technologies types. Once any increases by 1, you get an innovation. Here the really interesting part comes in: for each tech type (military, civic, religious and oratory) you have different tech trees where you can spend innovations for various bonuses. Some are minor, some innovations unlock laws or mechanics and some are just strong modifiers. Across all four types there is not even close to enough playing time to ever unlock everything (mods can change that obviously). That means that you can tailor your game to your needs or to your narrative (if roleplaying f.ex.)
I love building roads and the beautiful map. Very satisfying to watch cities appear on the map and grow larger (based on population) and roads connecting them.
There are many different buildings and most have an actual purpose (some are a bit too weak to matter sadly; looking at you market place and earthwork).
To me the building makes peace time play a lot more interesting (I like peace time and I do not enjoy endless wars without any breaks; soem are fun from time to time though)
There are some characters, but they aren't as deep or as important as in the CK series (I originally started with ck2). Their stats do matter: a high zeal stat tends to make your national stability higher than someones with a low stat and a high finesse stat makes building cheaper (did I say already that I like buildings stuff?)
In monarchies the royal family can be interacted with (marriages f.ex.) and I personally do enjoy that quite a bit. There also 6 bloodlines in vanilla (): Aiakid (Epirus), Lagid (Egypt), Alkimachid (Thrace), Antiptarid (Macedon), Argead (best by far; Alexander's blood; found in Epirus and Macedon) and Seleukid (Seleukid Empire); mods make this specifially so much better though.
Stability is a lot more dynamic than eu4 (there is none in ck2 and I haven't played Vic2), but the effects of agressive expansion are more limited on your country.
I am sure other players will have different takes - that was mine.