James Cameron Lawsuit -- Sued for More than $2.5 BILLION For 'Avatar'

Turns out every sci-fi nerd on the planet had the idea for "Avatar" before James Cameron -- because the director is now being sued AGAIN for allegedly stealing the concept for the movie ... this time for more than $2 bil.

Bryant Moore -- a science fiction writer not-famous for his screenplays "Aquatica" and "Descendants: The Pollination" -- claims Cameron used the two screenplays as the basis for "Avatar."

In his lawsuit, Moore points out various similarities, including bioluminescent flora/plant life, unbreathable atmospheres, matriarch support of hero vs. heroine, spiritual connections to environment and reincarnation, appearance of mist in scene, sunlight to moonlight, crackling from gargantuan foliage, blue skin/green skin and battle scene on limbs/branches.

Moore is also going after 20th Century Fox and Cameron's production company. He wants more than $1.5 billion in actual damages and more than $1 bil in punitives.