make a nostalgia saving throw
No doubt I'll add this (D&D5) PDF to my collection.
The heyday for me was AD&D in the 80s. There was so much material in the rule books that it could play very differently if, for example, took note of the material components required for spells. Of course, we developed our own house rules based which actually used information in the rule books - an initiative system suddenly split fighters into plate & greatsword tanks vs leather & rapier swashbucklers, as a role choice without disadvantage to either.
I was going to list some of the other (obscure) RPGs we played during the 80s and 90s - but frankly the list is just too long, and would repeat what has been said in a lot of places.
Often, we just made up RPGs for settings, and rolled with it. There was a great long standing campaign set in the 1640s - started as a Musketeers game, and ended up in England during the Civil War. It was always the obsurd million-to-one chance occurances which stick in the memory - in the latter case one character who still used a bow managed a multiple-critical to take out a cannon.
On the other end of the "playability" scale was a WWI game - 30 minutes to roll up a character, detail their background, choose possessions, etc - and 1 minute in play to fail a saving throw when "going over the top"...