7/10 at best.
Hmmmm.... I have played all three Witchers and just about every other RPG ever released on a PC and I'm giving Witcher 3 7/10 if I'm generous. It's no Skyrim, that's for sure. I'm playing on a GTX Titan based rig, with a 4k monitor.
* Nice framerates, very nicely optimised.
* Stunning lighting
* Great landscapes and scenery
* Beautiful soundtrack
* Best texture work I've seen in some time, especially on skin.
* Clunky animation, especially running anims. Makes it hard to stop where/when you want to.
* Little skill required for a very repetitive combat model.
* Voice acting is awful in the main
* Script is stilted, B-movie stuff.
* Character is not tabula rasa, but we're given "moral choices" often.
* Gameplay feels a little dated and "on rails".
For a similar gameplay experience, done better, I think you're best off taking a look at Batman: Arkham Knight, Shadow of Mordor (my Game of the Year) or Assassins Creed Black Flag. If you want a more immersive RPG, head right back to Skyrim. The Witcher isn't a bad series, but it is over-hyped, and isn't "all that".