I guess to answer your question, I think the M16 is the best US Military Rifle. I also believe the M16 to be the best rifle in military service anywhere in the world. The question wasn't about my own faviorite, but out of everything you mention, I would rather have an M16 in combat at any time in American history.
The M1 was the best rifle of it's time by far, and was revoluntionary at the time.