I can't think of many cartridges that have been launched in the last 50 years that have been more successful than the .223...whether you want to attribute that to military use or not is moot. You could say the same for .308 and .30-06 and 9mm and .45 ACP.
I can't think of many cartridges launched in the last 50 years that are wildly more successful than the 7mm-08 either...
.300 Win Mag is about it...and the reason for that pretty much is, cartridges to fit all needs were developed not long after smokeless powder was developed. So anything else is just trying to reinvent the wheel
I don't believe that there has been a cartridge introduced in the last 50 years that has been more successful than the .223/5.56, and the fact that it was adopted by the military is not moot. That is the fact that explains its development, endurance and success. It is not incidental that the .45-70, .30-40 US, .308/7.62 NATO, .30-06, 9mm, and .45 ACP have the same type of heritage and success. Military adoption=commercial success in many cases, even if there might be a similar and arguably superior cartridge available. One example very germane to this argument is the .223 Remington vs. the .222 Remington Magnum. Performance edge to the .222 Rem Mag, with a longer neck for advantage for reloaders, yet which one is a commercial success? The one that is nearly identical to the 5.56. It has nothing to do with commercial marketing, I would say.
The name Remington is on both of those cartridges, both introduced within a couple of years of each other.
U.S. military adoption does not, of course, guarantee commercial success, but you get my point: it ups the odds.
I am not one to bag on Remington. I have no dog in that fight. But it is interesting to me that another cartridge Remington introduced that had arguable advantages in performance and case design over another, similar one introduced at the same time resulted in a commercial flop for Remington and a comparatively wild acceptance and success for the other company. I am, of course, referring to the .244 Remington vs. the .243 Winchester.
And that had nothing to do with the military.