I played through the entire Soulsborne series in order from start to finish twice in the past three years. The first time sweeping through all the games took a few months but it was very satisfying, and I still wasn't burnt out on Soulslikes and continued to play more for another month or so afterwards.

The second time through I flopped midway through the series, making it to DS2 before getting distracted by another game. Nothing against DS2; in fact, it's probably the Souls game I've beaten the most times.

DeS: Only officially beaten the game twice (that first marathon was the first time I had actually beaten it, but my PSN account has trophies dating back to the year of it's release; just never finished it back then.
DS1: I want to say maybe 3, but possibly 4.
DS2: When this came out I beat the game and continued to finish through a NG+ playthrough, and I've come back to it a couple times. So probably 4 full playthroughs.
Bloodborne: Twice. Once when it came out, and once during that first Soulslike marathon I did a few years back. However, the later playthrough contained the DLC which I played for the first time.
DS3: Just once. I've come back to it a couple times but there have always been other games in the way. This was not yet released at the time I played through the full series, but I think came out shortly after. Still haven't played the DLC, which is the only piece of Soulslike content I haven't played yet.

Sekiro: If you want to include this, I've beaten it once, and during that playthrough, fought every boss I could (I believe there was a couple bosses that require two playthroughs to get, so someday I'll have to do that)

I remember reading about DeS possibly in a magazine or something and loved the idea of a game being brutally difficult and unforgiving but still fair, and after playing the game, I found it far too difficult at first, but once the shield mechanics and dodge frames were understood, things become fairly straight-forward. Learning the dodge mechanics in a Souls game is probably what holds many first-time players back, as it is odd to think that you can roll straight into a mob and not get hit by their attack.