Witcher 3 is so well presentated! So many flashback moments and story moments that pick up, in a very well explaining why, the happenings of the past. I haven't played a second of Witcher 1 and 2 and never had the feeling to be missing something when I played through Witcher 3 - which was by FAAAAAAR the best open-world-RPG beside GTA V in the last 10 years IMO.
A very underrated thing I LOVED about Witcher 3 was the loading scren in which they summarized what you lately did in your playthrough. Amazing idea and great execution. I really wish more games would have or will pick it up. It's actually one of the biggest obstacles for me to continue playing big games like this: I have a tough time getting back into the deep immersive experience after not having played for a couple of days, let alone week. Witcher 3 makes it easy for you to be right back in it.
CD Project Red can't be praised enough for what they did with this game.