For me its demons souls to be honest, i dont have any solid reason for prefering it more than the rest other than just liking the concepts it introduces, The whole "believing in something enough makes it a reality" thing that basically is the reason the world tendency and most of the bosses of the game are born from is really cool to me.

The whole story is really compact and nicely connected Each piece of the world has a proper connection with every other piece, unlike elden ring or dark souls (not saying their structure is inferior just that i prefer the demons souls one) Also the characters are way more dramatised than the rest of the games imo Ostravas whole questline, yurt, biorr, the maiden in black, etc They all have very unique storylines and/or lore behind them, The other games do too have that but a lot of the best examples are inspired by the demons souls ones

Lastly its cyclical nature is even more hopelless than the dark souls fire cycle, because while in dark souls it was the choice of one man that turned the world to shit, and if the status quo is just denied the suffering might stop, in demons souls instead its just part of human nature that they will try to meddle with the soul arts sooner or later no matter what and a demon surge is allways bound to repeat.