Personally I would place Bloodborne over Witcher 3. Witcher 3 was amazing but I think one of its weaker areas was its combat and difficulty. The combat was pretty repetitive and easy and didn't feel that refined (the same couple of moves over and over easily got me through). Putting the game on hard mode actually just made the game more annoying rather than difficult - stuff breaking all the time, for instance. Then there was also the fact that, as a high level, random items found in treasure were usually always of a lower level or just complete junk. Crafting was really the only way. Saying that, the storytelling and world building was phenomenal.
Bloodborne was just bliss start to finish. Gameplay heaven with an awesome atmosphere.