They can totally use other story but keep gameplay, it's gameplay that make it stand out back then compare with other horror survival game like resident evil
Parasite Eve was like the love child between RPG and Survival and was like a step up in class above the Resident Evils. No disrespect to Capcom, similar but different, PE felt like the posh survival sibling with the different systems, inventory, atmosphere, lighting and OMG that OST.