witcher 3 is a good choice, tonnes of quest available even though you will be mainly following its storyline. i have a slight issue with the pacing and combat but thats minor compared to how much content they put into this game

with Skyrim or Fallout 4 you gain more freedom and mod capabilities, but generally the story and task are pretty substandard (to me). If youre getting Fallout 4 make sure you get Far Harbour DLC. Gunplay is much better in F4 compared to F3.

If you like a story focused RPG and dont mind a 2d world you can try Tyranny which is om 60% discount now.