Sony are currently ruling the roost with their 35mm full frame mirrorless. Fuji have built up a loyal following with their DX crop mirrorless cameras and Panasonic and Olympus have their MicroFourThirds.
Neither Canon or Nikon have muchs to show in the mirrorless range and certainly for Nikon, they have nothing. Currently the only thing selling for them is the high end D850 which is arguably the best full frame 35mm camera available today and the end D3400 which is almost always on sale.
I expect that both need a foothold soon in cropped mirrorless and full frame mirrorless.