I think it is a masterpiece. Never understood the complaints about the combat, I think it feels satisfying, and provides a decent amount of options for the player to choose their style, without becoming convoluted. Similarly to Skyrim, which I am also a fan of, it does a good job of encouraging the player to interact with the different mechanics without overwhelming them. The combat never gets difficult, but is it supposed to be?
What puts it above most other open world games, is the depth of the World, every side quest is extremely well written, and none of the content feels like filler. And it has Gwent!
I usually don't even like RPGs or Open World games, but The Witcher 3 is certainly an exception and one of all time favorite games.