NSW.
The "playing field" has been tipped towards Qld for well over a decade now in a failed attempt to keep them competitive (e.g. PNG'er Lam allowed to play for them, NSW home games regularly taken away, Matt Rogers forced to play for them on a technicality etc). Yet they have still been on the losing end of the count (from memory, their 3-0 victory under Fatty during the SL debacle, when SL players were ineligible?).
Other reasons: their history of low, whingeing, and dirty players (Wally, Shearer, O'Neill etc), their celebration of an overtly biased ref (Gommersal), my hatred of the Broncos (which is equally based on rational reasons), that the state was a Superleague stronghold, that they used to squeal every time a Kangaroos squad was selected.
Having said that, I don't think the current crop of players are quite as "hateable", but then again, they don't have the talent of their predecessors either!
I don't think anyone could argue with any of those reasons...