I was watching Tony Northrup compare the Sony 16-35mm f/2.8 GM lens to the Nikon 14-24mm f/2.8 and realized that the Nikon 14-24mm has been considered the highest quality wide-angle zoom for as long as I can remember.
But that has changed. DxOmark.com rates the Sony 16-35mm GM that was released about a year ago as the highest quality wide-angle zoom lens. It scores 42 overall with a sharpness of 34 when tested on a Sony A7RII. Its sharpness score is 10 points ahead of the nearest competitor which is the Canon 16-35mm f/2.8L III.