Huh. As it turns out, I own all three Dark Souls, Bloodborne, and Demon Souls (through PS+ for that one) and the only one I've beaten is Bloodborne, and the only one I haven't even tried is Dark Souls 2.
I bounced off of Demon Souls because I couldn't go back to the PS3 controller. I put a solid 10 hours or so into Dark Souls 1 on PC (with the appropriate game fixing mods), and I put about 5 hours into Dark Souls 3 on PS4 when it came out, and it didn't grab me.
I enjoyed that triumphant feeling of beating a boss in Bloodborne, be it on my first or second go, or on my eighteenth try, but it's such a time investment I don't think I can go that route again. I know they aren't that long of a game, but BB was bouncing around my head whenever I wasn't playing it. And as someone who's starting a company, as well as writes books on the side, I can't devote that much brain function to a game anymore.
But now I'm debating installing Dark Souls 2 that I got on the Humble Monthly earlier this year, and seeing if it gets its hooks in me.
Because apparently I'm stupid.