I’d have to disagree because of the weird areas it falters in. Bill was a great villain, but he was also extremely wasted and underutilized for so much of the show that his move in the end felt more random than it should have been. He arrived too early and wasn’t shown nearly enough to be properly considered an overarching villain.
The prophecy appears as though it had big intentions when they started, but had to scrap all of it for whatever reason. Making that entire moment seem like a fake “we totally planned this out” moment(the Llama sweater and Wendy as ice were especially misplaced).
And my biggest issue with the entire series comes from the first episode. It had this big moment when Dipper reads “you can’t trust anyone in Gravity Falls.” That was basically the series’s Chekov’s Gun, but they never actually fired. There is never an instance in the entire show where someone in the town truly wasn’t trustworthy in how they presented themselves to the Pines. Gideon was pretty openly antagonistic to them, the cops always seemed to be investigating them(and even then they’re aren’t evil), McGucket is trustworthy because he literally lost his mind, the list goes on. The only person who couldn’t be trusted at face value was Bill, who was the villain and wasn’t fully trusted to begin with(which brings up the issue that when he took over dipper it had never been previously established that he was good with codes, meaning dipper would have had no reason to ever assume bill could open the laptop)
I loved the show, but it had far too many shortcomings to take the number one spot IMO