If we're talking box office that's one thing, but in terms of quality I found both Titanic and Avatar over-rated.
More so Titanic because at least Avatar has its fun moments. Titanic really is a bore for the first 2 hours watching Jack and Rose fiddle fiddle one another. It doesn't actually get good till the ship hits the iceberg. They could have easily cut off an 1 hour or so off that movie.