Just saw Avatar last night and was amazed! 9/10 Life changing, no, but with the hype and spoilers and open discussion it is almost impossible to not have some kind of predetermined opinion of the movie. I haven't seen Fern Gully, but I thought it was very derivative of The Mission except a happier ending.
Star Wars was the only life changing movie for me. But looking back that was in completely different era, the effect that movie had will probably never be duplicated. It was the right movie at the right time. Not even Lucas could duplicate the impact of that movie if he had a 100 tries and a billion dollar budget.
LOTR life changing? Naaah... The movies that came close for me were the Dark Knight for the plot and superior acting and Avatar for the visuals. Make a movie with the best elements of those movies and that would be life changing for me. Oh yeah and I would have to stay away from the hype.