Just finished up Witcher 3. Moving on to Dark Souls 2 in a couple of days.
I've spent a lot of time thinking about why I didn't like W3. It's certainly not that it's bad game. On the contrary, it's extremely well-made with a huge, atmospheric world, a complex story, and a pretty deep RPG system. You could tell the developers really poured their hearts into this. ff somebody told me that it was their GOTY, I wouldn't argue. But try as I might, I just couldn't get myself to love it like I had expected.
Somebody else compared it to kind of blend between Skyrim and Mass Effect, and I think that's about right. Except that it combines the things I don't like about those games. W3 has an extremely clunky combat system. Maybe I'm spoiled for just having come off Bloodborne, but both titles feature shield-less melee combat relying on dodging and countering enemy attacks, and Bloodborne does that infinitely better than Witcher. Then again, Skyrim's combat also sucked and I enjoyed that game. But Skyrim had all kinds of stuff to explore, and you could create whatever kind of character you wanted -- a tank, a mage, a sneaky assassin, or big gay orc -- whereas in Witcher there isn't a whole lot off the main path, and you have to play as Geralt which dictates a certain playstyle. So to the extent that it's like Skyrim, it's Skyrim without the ability to explore and chart your own course.
Of course, you could say the same about Mass Effect. In Witcher, you have to play as Geralt, and in ME you have to play as Shepard. You could choose to be a nice guy or a ########, but your character is basically set in both games. And ME had very little exploration to speak of. But the combat was so great, it didn't matter. Especially on the higher difficulty levels, every encounter required using your abilities well and picking the right teammates for the circumstances. The fantastic combat system never would have carried over to a true open world game. Bloodborne and the Souls games are kind of the same -- they're highly linear, but the combat system makes those game awesome. Witcher just doesn't compare to those games IMO.
Again, this isn't to say that W3 is bad. If the main story reaches out and grabs you or if you happen to identify with Geralt and like the main playstyle of the game, it's probably pretty awesome. But for me personally, it was missing the stuff I really liked in comparable games and ended up feeling kind of flat as a result.