The issue with Buffalo is that all their truly high-end players (Thompson, Dahlin, Cozens, Power, etc.) are all in the NHL already and have multiple full NHL seasons under their belts. Yes, there's still a good prospect pool there with the Helenius' and Kulichs and Ostlunds and such, but there really isn't a game-breaker in their system. And yet, they still can't make the playoffs. Who in their system is going to get them over the hump into constant contention? I don't see it.
The thing I like about this style of ranking is that it's specifically tailored towards which team has the absolute highest potential in the future, rather than who is gonna make the playoffs first or who is going to be consistently a low-end playoff team for the next ten years. That's why Detroit is so low despite the fact that they're already a borderline playoff team and have a strong prospect system.
On the flip side, a team like SJ/Anaheim/Chicago has a ways to go but a clear path towards becoming a legit contender. They have clear-cut franchise 1Cs in Celebrini/Bedard/Carlsson, solid systems around them at all positions, and more time to accumulate additional high-end assets. That is to say, the Sharks are going to add either a third 1C prospect (Hagens), a 1D prospect (Schaefer), or a Matthew Tkachuk type of franchise winger (Martone) next summer, and that fact is somewhat built-in to this ranking. Ditto Chicago and Anaheim. The Sabres and Wings, for example, are not.
That's why Columbus is a confusingly low ranking to me. They have a franchise 1C in Fantilli at the same level as Carlsson and Celebrini, another potential franchise forward in Lindstrom, a bunch of early-twenties supporting forwards with proven NHL ability, and a nice collection of D prospects lead by Jiricek and Mateychuk. Plus, they're likely to add another top-10 pick next summer.
Similarly, NJ has a franchise forward in J. Hughes, a very high-end 2C in Hischier, and an embarrassment of riches in high-end teenage defensemen.
I digress. YMMV with these sorts of rankings depending on what you most value.