Many of those same developers will also be publishing those games on PC, and will likely already have to make certain effects toggleable or "slider-able".

If you simply downsample the textures as part of your pipeline, turn off some reflection maps, and a few other low hanging fruit effects you could easily bring the game down to the previous generation.

It's not flipping a switch, but it is not too hard and some of it the major 3d engines provide mechanisms for