I started with demons souls and I'm seriously debating getting the remaster on the PS5.
My favourite is Bloodborne I just love the gothic horror aesthetic and the rally system is so good
I love the blood effects and the armour and weapons are all very cool, the pizza cutter is my favourite weapon in the whole series.
There is a special place in my heart for dark souls 1 though it's my most provided game I've got copies on PS3 and 4 and PC as well as the remaster. It's just so good.