How is this determined? Do you have a reason for this order or is it just what feels good?
the single most format-changing card in it.
Close, but Catcher. imho
Except that CoL has the single most format-changing card in it.
Pachi.
Take Pachi out of ZPST. Or out of virtually any Mangezone variant. And you generally have bad decks.
both of these decks can now survive with eelektrik. even before eel, magnezone could play jirachi over pachi and be okay.
i think noble victories has to be #1 or at least 2. it changed the format too much. you have eviolite, kyurem, cobalion, terrakion, virizion, super rod, chandelure, eelektrik, N, victini, durant, etc. besides from the dragons and maybe a few trainers and other pokemon, BW is not that stellar. i'll give hgss credit because it holds our format together. also, CoL is definitely up there, because many cards were reprinted and are very playable.
In terms of pack value, BW might possibly be dead last. Almost EVERY good card in the set also exists as a promo (aside from Juniper, Reuniclus, and a few others). The format wouldn't lose much if the entire set were suddenly rotated out.