This January, several works from 1925 entered the public domain. There is a very long while to go before most artwork from the 70s enters the public domain.

Legally speaking, you would still need to get permission from the copyright holder to reproduce the artwork. However, the layout and geometry are fair game--those are not copyrighted. If the game has any unique mechanisms, the patents on those have long since expired (patents only last for 20 years).

Before 1976, developers of copyrightable material had to work harder to protect their interests. If a game was made before 1976 and has no visible copyright claim or other evidence that the manufacturer intended to protect the art through copyright, then you can ask your local intellectual property (IP) attorney about the possibilities. Note that the company being defunct (e.g., Genco) does not necessarily mean there is no owner of the IP they developed.
.................David Marston

There are a bunch of 70s stern back glasses where they forgot to put copyright on them, those are in the public domain

Night of the living Dead movie they forgot to put a copyright on, also in the public domain

I don't know if they mentioned it in the video, but that second game is Williams Grand Prix with different art

Night of The Flesh Eaters would have had it