The replayability is mainly about what alternatives there are to try specific builds, but after awhile the weapons feels kinda samey. Right now, there isn't a particular weapon I'm interested for DS1. Although DS1 had great amount of variations for weapons, later games provided more I believe. The weapons don't feel that much distinctive even if there is high quantity. There are various classes of weapons you can try out. Curved swords, straight swords, great swords, great curved swords, ultra great swords, hammers, great hammers, axes, great axes, katanas, whips, magic, pyromancy, and fists. Well, there is a lot, but Great weapons generally feels the same. I will never use whips or fists. I have done magic and pyromancy build already. 3-4 playthroughs would cover my interest. I'd do a Strength build and do a great weapons run, next would be magic only run, and then int/faith for pyromancy run that I'd use inflused straighswords, then dex to play with katanas and spears. That should pretty much cover everything for me. That's all the variations that interest me.
One the other hand, bloodborne has less quantity of weapons, but they are trick weapons which makes them worth trying out individually, and thus increases replayability, even if the game doesn't have as deep of RPG elements.
Also, I recently tried the New Londo Ruins, which always scares the crap out of me due to the dark areas with darkwraiths popping out of nowhere (in the pitched darkness) doing combos on you with infinate poise. Also the got damn ghost that pop through the walls that you can't hit through the walls. For some reason, this playthrough, I died a lot to them. The only area that's left over that' I'm interested in is the catacombs and the tomb of the giants, but I hate going through tomb of the giants without sunlight maggots, and obtraining it, I have to go through the most boring area of the game. And I'm already getting tired of using the katana. it's not a fun weapon for me.
I agree with you the level design is what makes DS1. If DS3 had same level of level design, it would excel in all departments because the combat and the weapon variations has evolved from DS1. I luv how From Soft generally starts out, they generally start out in castles or something, and it's really interesting mazes, and then it starts to take a dive at some point. I prefer the whole game to be mazes inside castles, or places like blight town or the valley of defilement.
What I like best about From Software is the places makes you feel lost while exploring, and then you find a shortcut to make you feel relieved to know where you are. It's a great level design.