It really seems to be important that the word 'gun' is actually used or implied. There is an assumption that the gun configuration has a classic appearance. I believe there can also be a best bolt action sporter, or a best rook rifle, but not a best pump or lever action that's generally acknowledged.

Enginnering differences seem to turn to descriptive terms and other academic discussions, but "best" seems to be related to execution. It's only opinion, but there are some AR and bench rifle builders easily doing best work.