The upshot of this conversation to my ears is not the worst-kept secret that the MK is the worst Disney park in the world (the absolute truth... I spent half a day there on a five day trip, and I cannot stop thinking about how appalling my experience in Be Our Guest was - an immersive restaurant doesn't make up for some of the worst and most expensive dining I have ever had), but that respected people are consistently choosing HKDL as the worst or second-worst castle park. (Even though I get the strong implication from WDW1974 that there's a big gap between No. 4 and No. 5).
Not trying to be controversial here, but (both at the time and with hindsight... and the benefit of having seen TDL and its evening 50-minute-queue Fastpass Fiascos) I have it in my mind as #1. It may be smaller than the others, but it's immersive and immaculate everywhere you look (I admit being the youngest park helps there, but on the flip side, they're on top of refurbishments). Not only that, the lands are still true to their original themes and come alive beautifully at night (Adventureland in particular).
I wonder if people are marking it down for what it doesn't have (Pirates, Haunted Mansion, Big Thunder, Peter Pan's Flight). Perhaps... but the attractions it has in-place are no less impressive. I give it extra points for creating something original and not sticking to the 'tried and tested' formula. It also has some of the best dining - with "real-world quality" - within the gates of any Magic Kingdom park I've visited.
Its setting with the castle against those mountains, and the beautiful (and fully-walkable) resort that surrounds it (that fountain...) only go to further elevate the park in my eyes. Perhaps the fact it's a castle park evokes a misplaced nostalgia in guests familiar with DL/WDW (which is then not fulfilled because of the missing elements), but if you eliminate nostalgia and just look at quality, it's right at the top for me.