The M4A1 is most definately not 50 year old material. Nor is the M9, M1A2 Abrams (granted those are recycled), M249, and LAWs 66 and 80, Blackhawks, Apaches, and Super Cobras. Let's not forget the M95, M107, or M134. M40A4s are also not 50+ years old, since those are all still made by hand. M203s are, but those work well enough to stay in service. M16s have gone through so many evolutions as to hardly be the 1960s models in anything but name. M60s are still used because they work, and work well. We've retired most of our older ships, and our current ships are some of the best in the world (though, granted, most 1st rate navies don't engage each other that often, so there isn't really a benchmark).
Universally, the US has the "best" military in the world, though I freely admit that other countries best us in one way or another. There just isn't one that bests us in all of them, or even half of them (I realize "them" is a nebulous term here, but you know what I mean).