I suspect that there is more .22 LR produced than any other round and maybe as much .22 as all others together. Of the center fire rounds my gut instinct is that 9mm is the most produced round. Rumor has it some production lines are barely able to keep up. If or when we are out of middle east I'm sure that would change.
Ammunition seems to be somewhat of a commodity. During the first Gulf War at least around here 9mm was very scarce but .45 was easily found. A year ago that was opposite.
I never talked to anyone who had to fire their gun who said "I wished I had the smaller gun and fewer rounds with me" Just because you find a hundred people who agree with you on the internet does not mean you're right.