You might be asking the wrong question. For example, the set of papers satisfying your first question:
What are the most important or personally influential academic papers you've ever read? (call this set A)
has almost no overlap with what I would consider the set of papers satisfying:
Which ones are essential (or just good) for an informed person to have read? (call this set B)
And this is for a couple of reasons. Scientific papers are written to communicate, "We have evidence of a result--here is our evidence, here is our result." with fairly minimal grounding of where that result stands within the broader scientific literature. Yes, there's an introduction section usually filled with a bunch of citations, and yes there's a conclusion section, but papers are (at least in my field) usually directed at people that are already experts in what the paper is being written about (unless that paper is a review article).
And this is okay. Scientific papers are essentially rapid communications. They're a condensed, "I did this!". Sometimes they're particularly well written and land in category A above. But I can't think of a single paper in my A column that I'd want a layman to read. None of them would make any sense to an "informed" layman.
My B column would probably have really good popular books written by experts--something like Quantum Computing Since Democritus, or, like others have said, introductory level textbooks.
rapid
LOL.
In line with my continuing self eduction...
What are the most important or personally influential academic papers you've ever read? Which ones are essential (or just good) for an informed person to have read?
Is there any body of research of which you found the original papers much more valuable than than the popularizations or secondary sources (Wikipedia articles, textbook write ups, ect.), for any reason? What was that reason? Does anyone have a good heuristic for when it is important to "go to the source" and when someone else's summation will do? I have theoretical preference for reading the original research, since if I need to evaluate an idea's merit, reading what others in that field read (instead of the simplified versions) seems like a good idea, but it has the downside of being harder and more time-consuming.
I have wondered if the only reason to bother with technical sounding papers that are hard to understand is that you have to read them (or pretend to read them) in order to cite them.