And I'm not sure that your hypothesis is correct, could be, but definitely isn't the case with me. I've been accused of being a "book purist" on here but it simply isn't true and I think some people use that label on here when they don't like to hear criticisms of the show. I've only read the books once and don't remember some of the details. It seems that you are implying the writing on the GoT TV writing is on par or better than the Sopranos which I couldn't disagree more with.
It simply comes down to this for me - The show, thus far, just isn't that entertaining or interesting, regardless of source material or comparisons to it. And the reasons for it - The writing, the writing, the writing, the pacing and direction (constant ADD jumping from scene to scene, etc.). Some of the casting and acting have been great though. But I stated last year that if I HADN'T read the books I would've stopped watching it already, the show is that middle of the road and mediocre in a lot of ways. But again, some fans are loving it which is cool.
I'm not sure I'm communicating my argument very well, or maybe we're just never going to see eye to eye. I just simply haven't seen a single person who hasn't read the books who didn't like the writing, etc. I have yet to see a suggestion of better writing of an adaptation.
So I think my hypothesis has a lot of evidence behind it. You don't have to be a book purist to downgrade something because of known comparison. But I don't think we're ever going to agree on it. I would like to see you provide an adaptation you think that has been done significantly better -- I mean, if GOT is so poorly done, there's got to be better ones, right?
As for the Sopranos, I enjoyed it, but let's not make it more than it was. It was nice, highly repetitive, and frankly the "psychological family drama" aspect of it referenced by another poster was never very interesting to me. Frankly, both kids were shallow and the show did seven seasons of junxtaposing Tony's soft side with brutal violence. Over and over.
If you don't see anything deeper in GOT, I'd suggest you look deeper. Maybe it's not your angle, but the thematics on power, abuse of power, the necessities of ruling are all things that interest me. There's direct analogues to modern politics -- there's no doubt that Martin's view that Ned Stark could never survive comes from his views of modern politics and the simple fact that someone playing at that level of power never has their hands clean. (And when we get to book five... Dany as an occupying force -- wonder what could have influenced how that turned out?)
Anyway, there's 9,000 movies and tv shows a year that cover dysfunctional, unhappy, suburban families. Sopranos was a great show, but it had its share of poor pacing (there were whole seasons that might have been unnecessary). I don't even know if I'd say Game of Thrones is better (and The Wire is still the best show I've ever seen), but I don't think these are nearly as separate as people would make them out.
GOT is dealing with a lot of things that the Sopranos never had to. Two of the biggest are scale -- Sopranos is nowhere near the scale of GOT. The other is a necessary comparison to source material. The Wire had the scale of GOT in terms of characters, but not plotlines. But even so, they didn't have to deal with concerns about people complaining that a character was marginalized for time or simplicity.
D&D have a much harder job than the rest of these writers did in a lot of ways.
I don't really have any problem with people listing three to five of the best shows of all time as superior in writing, etc. I guess I haven't really seen any legitimate criticism to say the work is significantly worse, as you seem to be placing it. But maybe I'm misunderstanding you.