HBO has gotten really good at churning out superior television series by attracting great actors, dealing with mature content not suitable for regular TV, and lavishing high production values over the whole affair. It's too early to pass judgment on the new Game of Thrones series, but the first episode met my (wholly unreasonable) expectations.
Of course, so much of the first episode was obligatory that it's hard to know how much credit to give to the creators. If you've read the books, you knew exactly what scenes they would have to include to introduce the myriad characters and set the various plots in motion. If I were capable of stepping back and judging it through the eyes of an uninitiated viewer, I might say that the first episode teetered on the edge of being convoluted. However, as a fan of A Song of Ice and Fire, I'm thrilled that they don't seem to be cutting anything important.
Die-hard fans have no doubt been talking about the casting of the series for months now, but with so many of the actors being newcomers, it's only now possible to get a better read. I have few complaints. As expected, Sean Bean (Ned Stark), Peter Dinklage (Tyrion), and Lena Headley (Cersei) were all well-suited to their roles. Nikolaj Coster-Waldau is promising as Jaime, though his hair style seems a bit anachronistic. I'm not as thrilled with Emilia Clarke, the actress who playing Daenerys, but she didn't have much to do in the first episode other than look pretty (which she did well enough).
Two minor caveats. One, this was a pilot used to sell the series to HBO, and the quality of a series often changes between the pilot and the second episode (usually for the better, but not always). And two, due to the sheer number of characters in the story, some of the major ones got hardly any screen time in the first episode, so it remains to be seen how well the actors in those roles will handle the parts.
Still, if you're a fan of George RR Martin's novels, or fantasy in general, I think you have to be happy. The only person who might not be happy right now is Martin himself. He's about to get more fans, and that means more pressure to finish the damn books.