Yesterday I completed Demon's Souls, my first ever actual Souls game, having previously only played (and adored) Bloodborne and Elden Ring.
Good game, although definitely of its time, and held back by some really bizarre and opaque systems (opaque even for FromSoft), but lays the foundations for arguably one of the best developers going. I was overall disappointed by the bosses, with only 2/3 of them offering any serious challenge, the rest seemed overly reliant on gimmicks over difficulty, but the levels themselves were all mostly fantastic (with the exception of the poison swamp, obvs).
A friend of mine once said it's the best 7/10 game of all time, and I'm inclined to agree, because it's definitely hampered by its numerous drawbacks, but it sinks it's teeth in like only FromSoft can.