Only played number 2 and 3 and didn't really like 2 much. Though i'm going to try to replay 2 again one day.
I like that game and I really would like to play it more and complete it, but it's PC only and that is the most difficult part for me. I hate to play with mouse and because I'm having back problems and lousy laptop, it's a bit difficult to play since I don't have a proper table and chair. And my laptop fan is screaming like crazy, so I can play only short periods at a time. Too early to say here what is my favorite quest.
I think comparing w3 to w2 is unfair. W2 was simply a more refined version of w1, whereby the formula did not change that much. They learned from there mistakes and fine tuned it perfectly. With w3 they essentially went back to the drawing board and had to start from scratch more or less as it was there first massive open world game. In that sense w3 should be compared to w1 as they were both the first of there kind. If CDPR make w4 and follow the same formula as the w3 they will have the benefit of Learning from there mistakes like they did with w2. They've even publicly acknowledged many of them. Overall I think the main story of tw2 was better but tw3 was a better overall rpg experience.
Going open world was the natural progression the game needed to take. There were too many loose ends in the books and games that needed to be tied off. I find the writing in the secondary missions were fantastic but for some reason they the script was lacking with regards the main plot. I find most Characters really well written in particular Geralt, Regis, Dijkstra and Triss. I found the writers did a great job with copying Sapkaowskis writing with regards to those characters. I found Yen's sharp wit from the books somewhat lacking in the game and most importantly I found Ciri's personality far too normal and bubbly for someone who's gone through the nightmares she's gone through. In the books we see how disturbed she became but in the game she was far too 2 dimensional and normal. TW3 is not perfect but the best of the bunch. Cannot get enough of it. There is a reason why so many have claimed that tw3 has redefined gaming and the rpg genre. In fact I do not remember a game receiving so much acclaim in recent memory. Well deserved imo.Well, it is not like they were forced to make the third game open world, it was a conscious design decision (perhaps in the hope that it will increase sales), so if it made the game worse in some ways, then the criticism for those is still fair. But many of the shortcomings of TW3 are not even the result of the open world, and some of the weakest parts of the story are almost entirely linear.
In my opinion, each game is also less of an RPG than the previous one, as the protagonist became increasingly pre-defined with his memories, relationships, etc. being brought back from the books - it is a design choice that favors "cinematic" value (as it is easier to write good dialogues and cutscenes when almost everything is pre-defined) over giving the players freedom to define the character with their choices. I guess that trend would continue in any future games, so I hope Geralt's story is really over and he will not appear again.
Some of the issues with Witcher 3 are simply the result of not enough time or resources to fully develop everything in the game (which could be seen as an indirect consequence of the open world), but others could be intentional to reach a wider audience, and again have nothing to do with the open world. Such as the usually simple quest design that relies mostly on the players using the witcher senses to follow clues (more of a storytelling device than actual "gameplay"), rather than investigating and solving problems on their own. Or the one-dimensional antagonists outside the Hearts of Stone expansion. Or the lack of impact from choices made in the previous games, something on which similar or less resources were spent than on the free DLCs. Or the game giving up the original design principle of giving the player choices where there is no clear good or evil - Witcher 3 tends to follow more of a "good/bitter-sweet/bad" formula, often guiding the player towards the "good" path with various clues.
So, while the third game is clearly the best in some ways, I would hesitate to call it "the" best. In the end, all three have different advantages and flaws, so it is not easy to choose.