Taking ‘old-school’ too far, I have made a ‘creepypasta’ horror game set in the 1970s. A child plays a primitive home game console, unaware that it’s being used as a portal by Interdimensional Demons!
While I tried to capture the look and feel of games from that time period, I still took a lot of liberties (or the demons did). For instance, I don’t think ‘checkpoints’ had been invented yet. Also, there are a lot more screens and sounds than would have been possible back then. And they didn’t bother making objects disappear after they’ve been used for their purpose (keys), or have safeguards for not getting shit stuck where you can’t reach it anymore.
But hey, this game’s demon-possessed. That’s an automatic graphical boost, right there.