I don't think that his ideas were all that fresh. Avatar's ideas were better delivered in Miyazaki's films (Cameron was inspired by Princess Mononoke for Avatar). It's world was very well realised but also quite limited. It's why it hasn't realy worked in all the other mediums Avatar has tried to expand to, like comics and video games.
If you want a fresh world with simple stories, the other franchise called Avatar is way more creative: Avatar The Last Airbender/ The Legend of Korra. There's a reason so many people still discuss Aang, Zuko, etc, but nobody realy talks about Jake Sully.
Luke wasn't that forgetable in the first Star Wars film either. Neither was Jack or Rose in Titanic.