You just have to remember W3 came first and the AC games have clearly taken inspiration from it. It still holds up well today on every level yet it's years old.
Frankly, I was disappointed by some of its elements and clunkiness at release so I wouldn't be so sure it holds up well for me. Many of those flaws were glossed over because, hey it's Witcher. It was a very decent game but the main story was badly handled and needlessly drawn out and it was hyped to no end. If I didn't like it back then, and it's the game's main selling point, then I obviously won't think much of it now.
It did came first and served as an inspiration for AC but AC is still it's own thing with parkour, historical settings etc. it's just more fun overall, albeit still flawed.
And it's actually CD Project who should be inspired by Ubi on how to make an epic, interesting map without hubs