Cameralabs.com tested three models of Nikon 85mm lenses and the Sigma 85/1.4 lens. The low-cost f/1.8 G-series Nikkor tested out really well.
Nikon 85mm comparison review | Cameralabs
Their conclusion on the f/1.8 model: "Taking all results in the center, DX-corner, and FX-corner plus my experience from many, many real-life shots into account I come to the following conclusions regarding sharpness and contrast:The Nikon AF-S 85/1.8G produces the best performance in the most consistent way. It is easy to focus optimally, shows very little magenta ghosting in high contrast situations and has very low spherical aberrations / coma. It also degrades surprisingly little from center to corner and when opening up the aperture. Plus it performs equally well at infinity or at portrait distances. Its only weakness is a slight dip in sharpness somewhere along the borders of the DX image circle."
If you look at the DxO Mark resolution tests, the 1.8G and the 1.4G were numbers two and one in terms of the best-performing lenses on the D800, along with some exotic stuff like the 200mm f/2 VR-G Mark II, and the new Zeiss 135/2 APO....so...I dunno...I've looked at sample photos from the f/1.4-G and own the 1.8 G...they both are good, high-res lenses. I still like the 85/1.4 AF-D for portraits, over the 1.8 G...the 1.8 G is so, so critically sharp though, if you want a lens that's really sharp, and pretty good at the edges at wide f/stops, the 1.8 G is a fabulous lens. I think the older AF-D lens is prettier for single-person photos, where having softer edges is kind of like a built-in focus vignette. I really do NOT see the value proposition of the 1.4-G over its smaller, lighter stable mate. I think the 1.8 G is the best value, by far. The 1.4-G is not all that much better than the 1.8-G is; the same thing with the 50mm G models...you can pay a lot more, but get hardly any improvement at all.