The Hurt Locker was a gripping, suspenseful, and sometimes horrifying trip into a very difficult subject. Avatar was a lavish, guessable, easily-accessible flagship for a new technology.

Cameron pretty much Had to keep the plot quite simple to boost ticket sales, as Avatar was the flagship for the new 3D, big sales mean it will be much easier for future 3D movies to get made. Cameron's reward is that he will now have (even greater?) free reign to do just about whatever he wants, huge budgets, amazing technology, etc.

 Bigelow's film allowed us to see many things, how soldiers can sometimes struggle to work with new team-members while dealing with the loss of former team-members,  very different leadership/combat style, very complicated relationships between US troops and Iraqi civilians (I Loved the educated man who wanted to talk with the soldier, but his wife comes in and kicks the soldier out because she is angry about the US' treatment of her husband and country).

 It also gave us some idea of the Wrenching change between the combat zone and The World, suddenly you're back home and expected to do normal things, but there are still many remnants of the warzone still in your head and body, and sometimes the sheer intensity of being at war is the only drive you have left, as we are challengingly faced with at the end of Hurt Locker.

 There was no such revelation in Avatar. It was a very good movie, I enjoyed the hell out of it, but the plot got quite predictable, whereas in Hurt Locker you had no idea what was going to happen. That made Locker a better movie for me, among other things.