oh man I've heard a lot about Dark Souls but never tried it! might give it a go someday.
I'm a huge fan of a series called .hack//G.U., a PS2 series, (.hack//IMOQ games came before it), it's about an online game that will affect the people playing it in real life, the characters, design, story and the music are all so magnificent I cannot put it in words!
other series that I'm big fan of are Persona (played persona 3 first, but loved persona 4 the most!), Tales of series (first and fav one will always be Tales of the Abyss! the newer ones are becoming kind of boring and linear), Kingdom Hearts, Devil May Cry, Resident Evil (fave was 4). there's also a PS2 game that is completely underrated and I think it deserves much more attention! called Sword of Etheria, I really enjoyed it! (almost all of my fav games and series are PS2 games haha it was a huge part of my life)