I like DeS the best mostly because it's the only game in the series where the quality is consistently high the whole way through. Bloodborne doesn't have any bad areas either and that's part of why I like it so much too, but it does have some where it feels like potential was wasted, like Byrgenwerth, the Lecture Building and the chalice dungeons (and that's coming from someone who liked the chalice dungeons more than I imagine most did).
I think DeS overall has the best level design and variety (in terms of bosses, enemies and levels) in the series. That's on top of it having a bunch of interesting stuff that FROM never attempted again, like character tendency, world tendency, the system that lets you rank co-op partners, and soul form - the equivalent of being undead in Dark Souls - actually having a purpose other than avoiding online play (like increasing your damage in relation to your character tendency). Some of these were better implemented than others, but DeS is the only game where you can find stuff like that all in one package.
Also, sometimes what isn't there is just as important as what is, which in this case for me is DeS' lack of covenants. Covenants have always been absolute shit since they were first introduced in Dark Souls and I'd rather they never implemented them at all.
>>14007578
Read this, it explains it all pretty neatly: http://demonssouls.wikidot.com/world-tendency
>why does everyone prattle on about it as the best thing Demon's Souls had to offer
Do they? I quite liked WT because of what a unique mechanic it was but I don't think I've ever read anyone else say that they do. I was under the imperssion that most people hated WT.