Did he have opportunities to escape house arrest or prosecution by compromising his principles? I agree that Wikileaks has broken a lot of important stories, but many outlets break important stories - I'd push back just as hard if someone told me that A. G. Sulzberger was one of the most important journalists in history.
I'm not intimately familiar with those three particular journalists, but it's far from unheard of for American journalists to go to jail protecting their principles. And I'd point out that it's even more common for them to argue for their principles in court, which Assange is trying his hardest to avoid.