First JPEG side by side comparison:

So how does the new Sony A7rIII stuck against the best camera from the competition? Imaging Resource writes:

The A7R III has a crispness to the blues in the eye that the other two seem to lack, resulting in a sort of grey overtone from both the Nikon and the Fuji. What may be the most impressive is how well the new Sony FE 24-105 f/4 hangs with Nikon’s new 24-70mm and Fuji’s 63mm. 

I think that with exception of the Canon the other cameras are really pretty darn close. The biggest issue I see now is that it’s hard to justify the high price tag of the GFX. I think the difference will be more obvious once the GFX-100 gets released.

Preorders:
Sony A7rIII at Amazon, Bhphoto, Adorama, BuyDig, FocusCamera, Calumet DE, Wex UK. Sony Australia.
Sony 24-105mm at Amazon, Bhphoto, Adorama, BuyDig, FocusCamera, Calumet DE, Wex UK.