Dog: most of the stuff we talk about on this forum falls into the "Do we really care" category it's just something to talk about among guys who appreciate guns. not a big deal really.
No disrespect intended to the OP. Yes, much of what we discuss sometimes (often?) falls into the realm of frivolous (I may have spawned a few of these threads myself), but talking about sales numbers of consumer products is vastly different than discussing, say, ballistics performance of centerfire rifle cartridges, tactical considerations for civilian concealed carry, pros and cons of different types of rifle slings, etc.
Best selling among long-time gun collectors or very experienced competitors? Those models might be of interest to me.
Low cost models, or those that sell quickly due to a hefty advertising budget?
I'd then add, best-selling among first time gun buyers. Or best selling by price point. Best selling by buyer demographics (urban, rurual, age, profession, married/single, gender, minority group). Best selling among former military, law enforcement. Overall sales figures, in this day of targeted marketing, product placement in motion pictures and television, how a brand acquired its initial market share (i.e., Glock's entry into the law enforcement market), which pistols are widely issued to LE and/or military, really can be widely open for interpretation depending on how the data is broken down and presented.
My comment was not meant to invalidate the thread premise, only to state my position that the concept of best-selling is really meaningless in our society and often has nothing to do with a product's overall effectiveness, ease of use, overall quality, long-term reliability, durability under hard use conditions, and yes, overall aesthetics to would-be buyers. Best-selling is typically a measure of marketing and pricing, and the average first-time handgun buyer is almost always making a compromise with his/her purchase and isn't usually armed with the experience or knowledge to know better.