Alright, I'll try (haven't read all of them, saving some for retirement):
Book 1:
1st place: Burnt Offering (Rise of the Runelords): It's got everything, from oldschool dungeon crawling to high fantasy forgotten temples, even a bit of horror with monster in a closet trope and dark rituals and what's not. It's the MCU Iron Man for PF Adventures.
2st place: Edge of Anarchy (Curse of the Crimson Throne): The way to hook the players in, the early villains and how the story unfolds are just awesome. I always play the BBG early on as a victim of circumstances and drips her into madness and evil only in the final scene.
Noteworthy: Hell's Bright Shadow (Hell's Rebels): It's gives the 2nd place a run for its money. Also best PF villain ever imo.
Book 2:
1st place: The Shackled Hut (Reign of Winter): This one emphasize the best parts in Reign of Winter, the Russian-like feel, the scary fey-like nature of everything, the shapeshifting Winter Wolves, to hags, trolls and even a dragon.
2nd place: The Thrushmoor Terror (Strange Eons): This one feels like it's the best example of how to drive the notion of 'unwelcomed strangers' to its pick. The cult is awesome and scary, the detective work is great, the monsters are scarry and the fact that the PCs don't remember make it REALLY easy to modify as one see fit to enhance backstories and what's not. This one is the best opportunity to make PCs of all kind to feel like real people and not just character sheets.
Noteworthy: Seven Days to the Grave (Curse of the Crimson Throne). I am not a fan of ailments in PF, they are so easily removed, but if there's ever been an adventure that force you to feel the old-school scare of plagues, this one does. Most of the encounters work very well as well.
Book 3:
1st place: The Hook Mountain Massacre (Rise of the Runelords): The most scary adventure of the OS PF, and the most rounded. It has a clear start, middle and finish - with nasty encounters, first 'Better run and not fight it' encounter that is brought to the PCs (and while I usually not a fan, it does make the setting feel 'bigger' than just what's going on with the PCs). Horrid, funny, vicious, tragic. Love it.
2nd place: The Armageddon echo (Second Darkness). While it needed much revisiting with PF rules, the theme itself - of a trench war between elves and a race that was considered a myth is intense, the fact that you're not only fighting the Drow but vicious allies like Demons and an Aboleth was also welcomed and the visit to the echo of the distant past was the final chef's touch.
Noteworthy: Runeplague (Return of the Runelords) - I considered very hard if I wanna place this one here, but decided to go with it cause it hit all the right notes.
Book 4:
1st place: A Song Of Silver (Hell's Rebels) - It also got everything. Evil vs Good to the best of both abilities, the PCs reap the fruits of their efforts early on in the AP (and then comes the several twists in the end) and the best villain, again, in Paizo entire legacy.
2nd place: Valley of the Brain Collectors (Iron Gods) - Bring them critters in! the Brain collectors rule supreme as antagonist, and spread in some other nasty aberrations and you got yourself a fine piece of instant horror sci-fi fantasy adventure.
Noteworthy: Blood For Blood (Kingmaker) while not the best of what this AP had to offer, it truly stands out as the PCs kingdom becomes truly their own, as adversaries, both wicked or just crazy, threaten them all.
Book 5:
1st place: Tide of Honor (Jade Regent) I think this is the true beginning of the PCs purpose in this AP. Until now they were basically traveling - this is where they suppose to work, and while I could expand this book to 300% of its content and still I won't feel fulfilled, the missions with the missing Geisha, the barbarian warlord and the evil Daiymo just strike as close as one can get in high level Adenture.
2nd place: Doorway to the Red Star (Strength of Thousands) I know it's an unpopular choice but I really dig how the PCs come to this place in the AP, and the fact they are able to face legendary threats in such exotic ways and still stick to the landing is impressive.
noteworthy : The Price Of Infamy (Skulls and Shackles) finally the PCs coming full circle and hunt down the man who was a pain their side for so long. The fact that he conspire against the whole isles with the devils of Cheliax is just a bonus.
Book 6:
1st place: The Six-Legend Soul (War for the Crown) I wasn't a fan to all of the AP, but the ending is just magnificent. The final chapter of the most political adventure turns to an epic conclusion of a story of not just the PCs their friends and enemies, but the whole nation.
2nd place: Midwives to Death (Tyrant's Grasp) The end of PF1 truly feels like and ending more than any other AP. Almost like saying goodbye to an old friend.
Noteworthy: Rise of New Thassilon (Return of the Runelords) As the only one of 2 1st Edition PF Adventures Path - this one felt much more fulfilling than WOTR. The whole run is a crazy one but this one hit home.
