I strongly believe that anyone, with enough help from the collective knowledge here on the board and on ARFcom, can build an AR15 that rivals any of the brand names.
That being said, I must also mention that the proper parts must be used. No DPMS, only Armalite, Colt, Bushmaster, Diemaco. CMT uppers are to spec. The proper tools must be employed, nothing makeshift. If one has ANY DOUBTS about whether or not they're doing something right, they should contact those in the "Know" immediately.
As someone on here once said, a retarded monkey can build an AR15.
ABCD. Armalite, Bushmaster, Colt, Diemaco. US Contractors are good, too.