A good way to judge this question may be, "how long has it served?" How long will it serve.
1911- present, 101 years and still going strong
870- 60 years with no end in sight
BAR- 1918 through Vietnam? (a real man's gun)
The Mauser rifle series, which many bolt action rifles are still based
AK-47 Although an newcomer, it the largest production, and maybe the best battle rifle, ever!
Because I love them, I am adding a 6th. Mosin Nagant 1891- present.
Many or most of new arms Americans are buying now will be relegated to the scrap-pile of history.