best scopes for what purpose?
close (<100m) Eotech. Maybe not the best, but my favorite. Rugged, dependable, hold their zero REALLY well, GREAT reticles
far: Leupold, Zeiss, or Nikon. Far optics are all about the quality of the glass. there's no shame in buying a good scope that costs 2 or 3x as much as the rifle you mount it on.
PS big nod to Trijicon for the ACOG. The Fiber optic model the army and marines bought is absoulte medium range tactical artwork.