I wouldn't recommend DS3 as your first entry, I'd recommend Elden Ring, you can make it as easy or hard as you like and it has the most freedom in all aspects of the souls formula.10 hours. 10 hours is what it takes, or at least for me without Bloodbornen, to understand what the hype is about. There is a difficulty curve there that once you surmount it and everything clicks, all the systems that feed into each other, the patience required, the immensely satisfying gameloop, the medtroidvania style map design, the tension of holding your EXP and the possibility of loosing it, the adrinaline inducing boss fight, the feeling of exileration when you beat a boss etc. I could go on and on but I'll not change your mind, the dedicated fan base should be enough to make you curious and invest the time to get over the initial hump. 

AC6 10/10
Dark Souls 3 9/10
Bloodborne 8/10
Elden Ring 8/10
Dark Souls 7/10
Demon's Souls 6/10

I did play the other AC games as a kid, but I got annihilated and don't really remember much other than that.

I played launch AC6 and the rush upon beating those ridiculous bosses and how cool it felt makes it my top FS game. I beat every mission and storyline and then stopped just short of the platinum.

The horrid frame pacing made Bloodborne unplayable for me. I was getting a headache. I love the setting and art but the gameplay just felt more Soulsy to me. Meh. The gun replaces the shield as the parry. I have watched LPs and through video the frame pacing issues don't come through but playing it. I was getting a severe headache.

1. Dark Souls III - 9.2/10
2. Bloodborne - 8.5/10
3. Elden Ring - 8.5/10
4. Dark Souls II: Scholar of the First Sin - 7.5/10
5. Sekiro: Shadows Die Twice - 7.5/10
6. Dark Souls Remastered - 7/10

Not played Demon's Souls yet (please port it to Steam Sony).

1. Sekiro (10/10) best game ever

2. Bloodborne (10/10)

3. Elden Ring (9.5/10) Too big and needs a side quests notes to saved where you can read somewhere, story is Ass.

4. Dark souls 3 (8/10)

Played dark souls 2 on 360 and it looked like mud and was janky as hell, I only got to the boss and turned it off.

You haven't played Demon?  I still love that game.

I haven't cause i read the bosses are too easy and i hate  unforgiving check points but i will play it at some point on ps5. I also love the much faster movements in the newer games.

Bosses are way easier, no doubt.  Check points are fair.  I love the game, shows where souls came from.  Holds up really well even today.

Demon Souls > Dark Souls 2 > Bloodborne > Dark Souls 1 > Elden Ring >> Dark Souls 3

My first souls was bloodborne and just feels so much faster then say dark souls 3, plus i like the horror vibe way more.

I love good challenging bosses  that take hours, i also love exploring as much as possible to make the boss fight easier, like getting flasks or even grinding a bit.