You need more insight.
In all seriousness, from a gameplay perspective Bloodborne is far better than the other Souls game, the other games were better in other areas, but certainly not mechanically, especially Dark Souls 2, which was very clunky compared to the other games (still better than 99% of the games in the market though).
Bloodborne also had the best world building and lore, Demon's and Dark 1 had much better NPCs though (especially Demon's), and Dark 2 had a lot more content than the other three games, significantly so. Magic builds weren't as obtuse as they were in Bloodborne as well.
Demon's is my personal favorite because it had the best combination of everything, but I still recognize Bloodborne as the best Souls game mechanically.