The very high amount polish in dialogue, tone, atmosphere and beautiful areas with a generally functional-to-decent combat system and RPG elements that are not solely small % buffs on attacks.
Basically, at that scale, it's a choice between well written stories with beautiful visuals and an interesting interaction with the game mechanics. Rarely both. Witcher 3 IMO does the first exceptionally well and the second decently, putting it above most games of its kind.
Also, Gwent.
I do generally think that people gloss over the combat not being something particularly good, mainly because most WRPGs with action combat systems suck at that.