I don't have any figures but it seems to me that it must be; after all, we have far more topics to discuss than any other genera of firearm...
Just think about it: the AR platform is currently the most proven, most refined, most used military weapon that is also available to civillians. New components and accessories are continually being developed for the AR (and cannot it be said that we here are at least partly driving this phenomena); can that be said about any other gun?
In the modern world the AK just doesn't cut it...can't mount rails securely, limited barrel options, etc...And no other rifle is even close in terms of users. HK, AUG, all those others, are just non-viable, because the AR has the momentum, and is perfect for the M. Edwards Demming strategy of continuous improvement.
So what else is out there?
Hunting? Lots of hunters, yeah, but what do they have to talk about? Gutpiles and the .270 vs. the 30-06? The one that got away? Those people mostly buy guns stock and never change anything. They see things As They Are, while we here see things and say It Could Be Better, and My Accessory Is Better Than Yours.
What's left? "Snipers" or match shooters? Okay there might be something there, but they are overspecialized, like Praying Mantisses. The AR can be a precision weapon, or it can be a Kugelspritzer. And, I'll bet there a lot of posers on sniper boards, continually lying about group size...
Whats left? Cowboy action shooters? Meh. Reloaders? Booor-ing...Airsoft/Paintball? Ack!
If we have power, we should use it.