Well, remember fantasy gaming has non-rpg products. There was a Zelda tie in book that hung around in there for a long time, and sexy truth or dare shows up around Valentines day.
But also, in the 4E era more recent products where top sellers, what is notable here is lock of the core products.
Its certainly the cheapest way to buy it. But we know from IVC that D&D also dominates retail, and there has been a growth of millions in retail sales for RPGs. Most of that has to be core books...its not like there is much else to buy for D&D.
But let us resume our standard discussion.
We know from past threads that 5E has demolished 3.5 and 4E in terms of Amazon sales rankings, and almost certainly more books are sold through Amazon now then then. So a higher relative ranking must account for much higher relative sales. Plus, remember that growth on the retail side.
So I am calling it: 5E way better then 3.5 or 4E.
But thats a low bar you say, and you are right.
What about 3E? That was supposed to be huge out the gate. But just 3 years later they launched 3.5. Hmm, 3...years...later.
We know it was launched to make up for lagging sales. 5E sales aren't lagging, by some measures they are growing.
So I will say it 5E > 3E.
Ok, 2E. We know that was a lackluster edition. 3E > 2E. Hence 5E > 2E.
That leaves the big boy: 1E. And I can't call it. Sales in the early 80s where insane, and it was kept in print for a really long time. Of course the Blume brothers wasted a bunch of that money (and there was Gygax, living it up in Hollywood), but that is another thread.
Still, the best selling edition in decades. And on its way to best selling of all time, if not already.