Personally I'd just leave it as it is until (if) you get genuine requests to remove particular content from resepctive copyright holders. Sure, some of it is technically piracy, but as you mentioned a lot of the stuff thier simply isnt available to buy anymore, so it's not like youre costing anyone money for 99% of the content. The KS ROM images are probably the main exception here, and the things you're most likely to get genuine requests to remove.
Im reluctant to use the phrase, but it is a bit of a grey area in some ways. Legally its fairly black and white, but with a lot of software that is still copyrighted some of the companies dont even exist anymore, or have simply forgotten about some of thier software for non mainstream options from last centuary, or possibly even unaware theyre the copyright holders to some software (from when mergers or buyouts, etc. happen).