I can’t honestly tell you what my final clock time landed on upon first finishing Demon’s Souls, while it felt like I didn’t spent an enormous amount of time getting to the end, I also has way more free time to do so, so it was probably up there.
It’s interesting you bounced off of the other Souls games but landed on 2, it’s certainly the most different out of the group (not including how they changed fundamental gameplay things come Bloodborne).
It’s a much slower game than its counterparts, no longer were you able to sprint, dodgeroll and parry your way through every silver knight, hollow thief and butcher you saw, but expected timing and a more defensive style.
Enemies would poise through your attacks, track your movement with their swings so you couldn’t just spam dodge, your overall speed was slowed down and the parry / riposte mechanic came at a much higher risk and difficulty once enemies could delay their attacks.
A lot of original Souls fans hated how different it felt, but speaking for myself in hindsight, I warmed up to the game when I just take it as its own thing. Nothing in the series has really topped the art and level design of Dks1 for me, combined with its more deliberate and sharp movement and feel, and, in my mind, a much more interesting story it still hasn’t been dethroned.
I’d encourage you to jump into the Dks2 DLC, I’ve heard good things, but I’d also urge you to revisit the other souls games now that you’ve finished your first game in the series.
While I really like Demon’s Souls, it might be a tiny bit archaic to go back to, but it’s a game that drips with atmosphere, has great boss designs, and an interesting world.
Dark Souls 1 is probably my main recommendation (in any Souls conversation really) and if you’re having issues with the game I would suggest checking EpicNameBro’s channel on YouTube for a comprehensible playthrough of the game “From the Dark” featuring both gameplay tactics, story / lore introspection, fun different builds and NPC quest-lines.
If you have a Ps4 I’d highly recommend Bloodborne too, a much more aggressively playing game but strangely enough I just think it makes it more accessible. It’s the best looking game out of the series; the monster designs are great, so are all the bosses. Moving the parry mechanic to a ranged attack was a great move which lowers the risk of taking a hit and makes it a more prominent feature in your arsenal out of the gate.
I guess it’ll kind of depend on whether you want to stick with medieval fantasy or want to explore a lovecraftian horror setting for your Souls game.
As for Dark Souls 3, it’s probably the best feeling Dark Souls game, finding a middle-point between Dks1 and Dks2.
It’s got rather linear yet branching level design but the structure and geography of the levels are still good.
All of its elements separately pull it in different directions between DeS, Dks1, Dks2 and BB, so it kind of feels like a best-of (especially with all the references and cameos).
I’ll say it gets a bit light-attack spammy with how easily enemies tend to stagger in it, and the enemies like to perform the same frantic attack pattern. Dks3 is still very fun and very polished, I’m sure you’ll have a good time with it.
That’s my overly long response to a simple question, hope any of it helps.