I'd recommend the Metal Gear series but depending on how thorough you want to be you might have some trouble playing them all on modern hardware. Same goes for the Silent Hill series.
Resident Evil and DMC are pretty good suggestions. Although I totally think you should play the black sheep in the series too. Just so you have the whole picture.
Kingdom Hearts would also be interesting. That series is silly and mostly decent to quite good. And it's very entertaining to see all the bullshit lore and worldbuilding Nomura and Nojima got away with without a Disney exec pulling them aside and saying "Please remember, you're making a Mickey Mouse game for children."
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