Yeah, based on retroclones and youtube channels, it seems to be B/X. To me this is a bit funny, because back in the 80s, it seemed that AD&D was far more popular than B/X. Usually B/X was the gateway to AD&D; at least where I lived, though most of us really played a mash-up of the two. I had one good friend who preferred BECMI so we ran a multi-year campaign of that, making it to the high companion levels with domains.
But these days, as evidenced by the wild success of OSE, it seems to be B/X that retains the dedicated fan base, largely for its simplicity and streamlined modularity.