Wow, Fox has given me yet another reason to hate them! And I was already spoilt for choice.
Fox can talk all they want about having the rights for 20 years, but just consider that. They sat on "Watchmen"... for 20 years. They had no intention of making this film. I'm sure the only possible benefit they saw in keeping the project, was that they knew it was a potentially great property that a studio that actually has balls would eventually make into a huge movie. And once said studio with balls made the movie, THEN Fox could exercise their claim to the movie to make a nice tidy profit. Someone else takes the risk, Fox gets the reward.
To put it simply, Fox are a bunch of greedy, soulless corporate scumbags.