So why does the movie have to be either "brilliant or bullshit"? That's an either-or fallacy big enough to bury Ganyon's whole village (gratuitous THE LEGEND OF BILL reference).

(I don't even like using such language; as Tolkien put it, that's just unnecessary orc-talk.)
I've yet to see AVATAR, and after having the scene of 10,000 Orcs charging in the rain permanently embedded in my mind thanks to LOTR, I'm not sure I ever will. Sometimes we forget that everything we witness, especially when it's something that striking, gets embedded in our memories and shapes our thinking from then on. I have enough trouble dealing with
fencing, for pity's sake. All-out warfare between a futuristic mechanized army and a primitive but effective organic one (and that's just from the preview I've seen)? No thank you. I don't get involved in computer gaming either, for the same reason. My imagination is vivid and sensitive enough as it is. It doesn't need to be put on steroids by visually oriented films on AVATAR's level.
I will say this: I LOVE the scene of an Earthlike planet (Pandora) orbiting a Jupiter-like planet. So evocative. That's not precisely a new idea either, but it's one that fascinates me.