I actually adore the personality system of Stellaris, even if only for the fact that it breaks the sci-fi mold.
Because let's take a look at let's say the Zerg. An endless sawrm of hungry bugs trying to absorb all organic life. What are the Tyranids of WH40k fame? Right, a sawrm of bugs that wants to absorb all organic life? The Cravers from Endless Space? Yep, bugs eating all organic life.
Meanwhile, your first contact in Stellaris may be a race of gigantic space-Mantisses. Your warships pre-heat their weapons, for your crew knows through decades of stagnant sci-fi that bugs ,mean trouble. But after establishing communication it quickly is revealed that those fearsome bugs are actually a democratic nation looking for allies.
On the other hand, you can run into cute little space foxes that only seek to exterminate all non-fox life in the galaxy. Heck, once I even ran into a Human Fallen Empire, which absolutely shattered the space 4X trope of humanity being new to the stars and being adaptive and whatnot (because most developers are humans), while these guys were a stagnnant, monolithic society of tech hoarders, that had "beaten the game" millenia ago, now having little but thinly veiled contempt for all the younger races falling over their feet trying to control the cosmos.
Another strength of the system is that it creates what are essentially highly unbalanced galaxies. Because let's take for example Civ V. In a large game, you due to the highly limited amount of civs (which are all mere caricatures anyway) will more often than not get a relatively balanced miy of AIs - some warmongers, some diplomats, some scientists. In Stellaris, you just might roll into a galaxy consisting of nothing but guys wanting to build federations, or a galaxy populated by nothing but what are essentialy Crusaders,
The problem is that it AI is too passive, not trying hard enough to achieve their goals. Alliances and federation should from much faster, and Zealots and Purifiers should wage far more wars.
Sectory are eh, on the one hand their AI needs a serious enhancement, at least they reliefe me from the atrocious planet micromanagement. If I am a Space Emperor, I do not care about what poweprlant is build one tile (4/5) on planet 29, or if my Corvettes use Blue Lasers or UV Lasers. I hire people that care so that I do no longer have to care.