hang-the-9 was correct in stating it depends on game settings [how much eye candy you want to see].
Personally, I suggest a GTX 1080. An AMD Vega will also do the job, however, it requires almost as much power from the wall as does a GTX 1080 Ti.
The following man tells the truth on YouTube. Please note the following Youtube review is using early drivers, and AMD drivers mature well over time. [I am using an MSI GTX 980 Ti Lightning, so, I am not an AMD fanboy].
https://www.youtube.com/watch?v=flekUCK9O2g