He had a lot of creative pull in the Hulk movie, and was viewed as "difficult" to work with. I don't think he's difficult I think he's really passionate about the projects he works on and wants them to be good creatively as much or more then financially. The bean counters in Hollywood only care bout the money. They only tolerate difficult actors if they are on Tom Cruise level etc. Marvel tried to lowball him for the Avengers and his agent was pissed and called them out on their bullshyt. Marvel is notoriously cheap. But I heard they really lowballed him because they didn't want him back as the Hulk and wanted a fresh start.
Norton a great actor though, so he's always work. But he's not sought after by studios. Normally it's big directors pushing to cast him. Like how Tony Gilroy pushed to cast him in Bourne
