ME had a problem with template design though, just like other Bioware games. ME2 fixed this a bit but at the expense of making the main story matter at all. And yeah ME3 lol.
I don't think any Bioware game has ever had this quality of writing though. Not even close. Then again they couldn't even touch TW1 or 2.
Mass Effect was good at coming up with likeable characters and then putting them into interesting situations. It resonated on such a wide scale because of its pretty accessible appeal; kind of like Star Wars. It grappled with a few deeper themes but never really beyond a surface level. It even had a blatant morality bar giving the player outright points in one direction or the other.
The Witcher takes a much more realistic approach. The world has a tactile grounding to it, a sense of amorality and real grit. That's what I think the other poster was praising and what Mass Effects didn't do.
I disagree both ME1, 2, and a good part of 3 are written very well. I think many people here are confusing good writing with their preference of one type of storytelling over another. It's like comparing Game of Thrones to Lord of the Rings or Star Wars with Star Trek, while these series may share the same genre their approach to storytelling is different. GoT/ASOIF, much like The Wticher series, is grounded in a much more "realistic" world. It's not so much about some hero stopping some great evil threat (at least not yet) but much more about the political machinations of the various Houses and characters and how individuals seek to maneuver or remove themselves from the "Game" in tact. On the other hand Lord of the Rings, Star Wars, and much of Mass Effect follows more closely with the mono-myth or the Hero's Journey, in which one main character and a group of characters confront some great evil and in doing so change the course of their world in addition to growing individually.
Neither storytelling is superior to the other, both can either be written poorly or written great. That said, many of us gamers have grown weary with the latter type of storytelling because it has been done so much, mainly because it is easily adaptable to gameplay format as opposed to "realistic" storytelling. But, that doesn't change the fact that ME is a very well written game. DA2 was BioWare's attempt to break from the mold but while it was ambitious and fresh they failed in its execution and thus I was disappointed though not surprised when they went back into their "safety zone" for Inquisition.
I've always liked this video which explains the type of storytelling TW series attempts:
https://www.youtube.com/watch?v=qRsqAmuxjNk