Warning long post. Who knows how long this thread has so I thought I'd throw in as many of my thoughts in one post as possible. Hopefully without writing an essay. I do have other opinions about this but I think this wraps up my major issues with DAI.
What I liked about TW3 and my comparison to DAI.
Protagonist
Geralt had a life, history, and his own story. Because of this I was able to connect to him as a person while at the same time shaping him as a character. Geralt also had a personal involvement in the events in the story. He had someone to protect, to care for. The stakes were high because they were high for him.
The Inquisitor had no life, history, or his own story. This made him very generic, a John Q Everyman so that everyone can pretend to be him. Therefore there is nothing unique about the IQ himself, nothing to draw me in to want to get to know him and how he relates to the world and the events around him. He has no personal stake. He's there to protect everyone.
The problem with protecting everyone is there is no personal stake in the matter, no "face" to anchor the IQ to events taking place. Even the Mass Effect team realized they needed to show Shepard's personal involvement and how the Reaper invasion affected him by using the little boy. Now, I would argue that it was poorly done. Which it was. But I understood their intent in ME3.
What TW3 does better than ME3 is make the "face" something far more tangible by making it someone the PC actually cares for. Ciri. For those of us who haven't read the books, we have no prior info about Ciri or how Geralt feels about her. So CDPR introduces us to Ciri through Geralt's dream. We see him train her, her interactions with the other Witchers, what life was probably like for them all when she was at Kaer Morhan. From this we know Ciri is important to him and the game reminds us at every turn by giving us special moments with Ciri, the hugs, the pep talks. These moments are what makes Ciri important and likeable to us the player as we experience Geralt and Ciri's relationship through Geralt's eyes.
The IQ has none of this to tie him to the story. He's a generic every day RPG PC.
Villain
I would say both games didn't do a good job of showing their villains but I think TW3's villains, The Wild Hunt, had a good reason for doing what they were doing.
Much better than Cory's rebuilding of Tevinter motivation. However, The Wild Hunt appeared strong and intelligent whereas Cory appeared reckless and silly. The only time Cory appears with great force is the attack on Haven. Afterwards the IQ is beating him and his "army" back like they are pestering flies moreso than a real threat.
Whenever we faced the Wild Hunt in TW3, it was at key moment in the story. Planning and preparation was needed before facing them in battle. They weren't just trash mobs scattered throughout the map. CDPR treated them with care and didn't saturate us with them to the point where we can just hand wave an encounter with them.
Side quests
If the main story is the meat then the side quests are the potatoes. TW3 gave us big freshly baked potatoes with cheese, bacon bits, and sour cream and chives on top. DAI gave us some little mini potatoes nuked in the microwave and didn't even bother handing us some butter.
TW3 side quests had character interactions, twists, atmosphere. A Witcher contract wasn't always JUST a contract. The conclusion wasn't always JUST the conclusion. The cut scenes focusing on the faces of the characters and not the back of Geralt's head aided us in connecting with them the way Geralt himself would, because we are seeing from his perspective. Take the first major Witcher contract you can have. The Ghost at the Well. When Geralt visits the man who posted the notice, the man brings you into the room as he's talking about his sick daughter, you then see her laying there ill with her mother tending to her. The man explains why he needs the ghost gone, she needs clean water because she can't keep anything else down. This connection is missing in DAI. Especially with a PC who is supposed to be centered on protecting everyone.
If I'm supposed to feel something for everyone, then at least show me the people I'm supposed to protect. Let me in on their lives and problems. Not give me a note in a ditch.
Player Choice
Continuing from the Ghost in the Well contract. When the man explains his problem, I as the player is left with a choice. To help, haggle, or take whatever deal he's willing to offer because helping him out is more important. None of these options scream "good" or "evil" these are just choices left up to the player to decide how to handle this particular situation. If you choose to haggle. Geralt explains that he feels for him, but this is a job for him, and you can proceed to haggle a better deal. In my first pt I got a good deal and helped him out. In my second pt the man refused to pay the amount I asked and I left and went on about my own business.
I don't know if there were any consequences for helping or not helping. However, for every seemingly minor side quest we have the Baron quest, which has been talked about to death so I won't get into it.
World
Once again something that has been spoken about a lot. DAI felt lifeless. You never get the sense that you're talking to real people. You never truly see how the hole in the sky affects anyone. They tell you they are afraid and that they need blankets et al but we're never shown the devastation. In TW3 we see the affects of war and the cruel acts by those in charge. We've also seen the good and bad by those on all sides.
Ex: You can take a Witcher contract to help find this guy's brother. We find him only to see that he was saved by an enemy soldier. We see that these are all just men making due with the decisions their leaders handed down to them. It doesn't mean everyone is reluctant to fight but not everyone is eager to spill blood mindlessly.
In DAI, the Red Templars are bad and the Venatori are bad. End of discussion. The only time we see some complexity is with Samson and Calpurnia.
Companions & Characters
DAI and TW3 have good companions and LIs. DAI certainly has more diversity. Which is good. The only problem is that I never felt like they were my IQ's real friends. It's not like ME and TW where we have a set PC. In DA we are constantly meeting new people for the first time so it's hard to feel close to them or see them as friends you can rely on. Actually DA2 did a good job of establishing the friendships and a lot of that had to do with showing us the passage of time and giving us a more personal story. Yeah, I know DA2 wasn't perfect not even in showing the passage of time but they at least tried.
I personally don't understand why people even want cameos in every DA game when it add nothing to the story at all. Seeing Kaidan in ME3 again is not the same as seeing Leliana again in DAI, and not the same as seeing Roche again in TW3.
Shepard has a past connection with Kaidan, we can continue Kaidan's story and friendship or form a new type of relationship. With Roche, we see what he's been up to and it hardly feels like prying. Over all, you are really catching up with an old friend/companion. With the IQ and Leliana, we meet her...again. Sure she has a story we can continue but that connection isn't there. You're not the Warden, the man or woman she had that great adventure with, formed a bond with et al. It's just not the same. It never feels like a true continuation and at worst the IQ seems like some nosy busy body and Leliana seems like she's regressed as a person.
Ending
TW3. Do I need to go on? Once again, they use their villains wisely and facing them requires planning and preparations. They don't just pop up randomly and we teleport to a random location to face off against an invisible army. Everything makes sense in the TW3 and the final fight is more personal. CDPR put some thought into how to tell their story overall. I may not agree with everything CDPR did but I know they put some thought into it. They didn't just check mark their list of assets, fill whatever quota they felt they needed to fill then called it a day. Geralt's story wasn't treated as an afterthought, some placecard to read. Hate him for being a fixed PC all you like, but you can't call him some run of mill RPG PC.
Well that's my full feedback. TL;DR.
The last time a game had a big impact on me was The Last of Us. I've played other games since then but none that made me care about the characters and story the way I do, until TW3.