Maybe Game of Thrones
I think the pilot was one of the worst episodes and I love the show and have read all the books.
Callin you all out for revisionism. Just the opening theme with the stuff that pops up was insane. Then they killed a major character in the first ten minutes but he survived. Plus you had Tyrion for the first time ever doing what Tyrion does.
It was a serviceable introduction, but I didn't get a sense for what the show would be until much later. I didn't at all take the Bran scene seriously. I was like "yeah, he's gonna be fine... typical fantasy schlock". I only kept watching, because people who read to books insisted the show was going to be unique. Initially, I just thought it was a wannabee "Lord of the Rings".
I think it's revisionism to claim that first episode was one of the best ever, because the series as a whole is one of the best ever.