I could literally start talking now and never shut up about this subject, because for me it feels as though there was just this endless gulf of games pre-NES that almost no-one talks about, and that the NES completely sucks the air out of the ‘older games’ discussion. So I’ll be brief!
One of my ancient thread that lived and died in January 2021 is this one about Synapse Software, a real highlight of the era (in my opinion). At some point I’ll go back and re-link all the links! I think if I had to pick one game with some real staying power and interest to modern game appreciators, it’s probably Shamus (and Shamus II, so 2 games). It’s got DNA from Stern’s Berzerk, a sort of maze game but also a shooting game. But it takes things one step further and requires you to backtrack with keys and so on, and as a result it ends up feeling like a proto-Legend of Zelda.
I should note that Shamus’s creator, Cathryn Mataga, was still active in game dev as of a decade ago (her company’s site is still live but no new games have been listed since 2012, so…)
Anyway, here’s some gameplay footage of most versions, including the extremely surprising Game Boy port.