I'd also like to note that villains, IMO, are the basis for a good story (if the story requires one). This tends to be my issue with many super hero movies, where the villains and sometimes their motivations are the weakest part of the entire conflict. Looking back on a lot of my favourite series and characters, I notice that I like villains more than heroes by a large stretch. Using your examples for instance, Darth Vader is my favourite SW character (with palpatine being a distant second).. why? Because without their presence, without their power and general demeanor, the show would lack a credible and believable threat. If handled badly the Sith wouldn't come across as the menace that the show tries to portray them as.
It's the same with GoT for me, Cercei and Geoffrey are two of my favorite characters because they make you hate them and it's difficult to get audiences to do that. I actually want Cercei to win the iron throne and Danny/Starks to lose, because I don't believe that they push the show forward as much as the villains do. That's not to say they are bad characters, but to me they are unappealing. I know that this isn't a very popular opinion many of the people who watch these shows, but for me at least, an action show/movie is only as good as its villains.
Yeah I agree in a sense that the villains should be elaborate in order for the story to be interesting, that's why I gave the contrast between comic books and modern series, like Negan in TDW, or even the new villain in GOT, Euron Greyjoy... His storyline is very interesting.
Well anyways, next season is gonna be the last one in GOT, and only 6 episodes, but they're working out on 4 preludes on the backstories of the characters, the aforementioned Euron Greyjoy, and the Rhaegar Targaryen "The mad king" and other cross-stories... It should be pretty interesting.
Euron's should be great and the portrayal of the baratheon led revolt should be good as well. I'm hoping that one of the prequels also dives into the "fall of the dragons" so to speak, so we can see why they are pretty much non existent.