This is all greatly dependent on what you grew up with, how simple or diffiicult you like games, what you like to work on, and what themes you are drawn to. I will try to break down each.

art - Pre
originality - Pre
fun factor - very subjective. I think it is Pre if you like simpler games and post if you enjoy deeper games.
replayability - also very subjective. I think it has more to do with specific shots (making them, getting close, or totally shanking them).
pure pinball bliss - There is no way to quantify this. It largely depends on what you grew up with, your sentimental connection, and your enjoyment in the theme.

Is the post dmd era actually better, or do we just like discussing it more?
All these games are newer...so they are fresher in peoples minds, are tied more to pop culture, were more widely available, and a lot of people just werent old enough to have played many games before...or even werent alive when they were made.

If there's one pin that most supports your choice please share.
Its hard to say one pin supports a choice because there are far too many out there.
Paragon is amazing, but so is JJP potc.

All this is why i always recommend a variety of pins from different eras in ANY home collection.

It seems to me that most people under 40 dont have much interest in EMs. They only want dmd and newer pins. I would be very interested to see an age chart on it, actually.

I very rarely see anyone under 60 interested in wood rails. There are, of course, exceptions to everything.