With 5E coming, I've been looking back at older editions trying to nail down an answer to the question "what is D&D to me?"

I revisited D&D by way of the Rules Cyclopedia and AD&D via the 2E PH and 1E DMG, and looked through my 3X stuff and then Pathfinder, and finally came back to take a look at fourth edition. 

What I found was pretty interesting, because it resonated strongly with what the developers of 5E are saying about every DM making his own ruleset. I found that no single edition of D&D was "My D&D" - because I never played any of them by the book. Rules were cleaned