One thing you have to remember is that both Titanic and Avatar have had several theatrical releases. Titanic boosted its box office with the 3D version, and was in cinemas for many, many months first time around. Avatar was re-released as an extended version and was also in cinemas for almost a year. Then they weren’t immediately available on home video, when TFA will be available in April. TFA has almost got there with just a over a month in cinemas. TFA could have many re-releases in the future that would count towards its box office. It would be interesting to see the actual figures for Avatar and Titanic on solely their initial release without any subsequent re-releases/ versions