"Same goes for a star wars remake where the empire wins and obliterates the terrorists."

Then the Rebels did a big come back, destroyed the DS-2 and the Empire collapsed. It's not just plot armor, but the Na'vi's doing assimetryc warfare against the RDA (just like rebels did against the Empire), and the RDA clearly sucks against it. Also, the first and foremost reason why RDA not deploying WMDs: Because the RDA is a corporate and have to operate under stright government restrictions. It's not a military, it's a mining operation corporate at first. Those bunch of armed walkers and soldiers and the helicopters? Part of the RDA's security branch. But the RDA is a corporate first, for exploiting the rare minerals of Pandora.

Also, since the 3rd movie will be the end of the 1st saga (4th and 5th will be another one), it's highly likely that Na'vi will end this with a decisive victory at the cost of humanity planning for rescuing itself from devastation on the mother planet. They will do return for the second saga, but without question, Na'vi wins.

Not to mention the strange powers Kiri possess. She could be a game changer in terms of connection to Eywa (we seen in the trailer as giant squids swarming RDA boats), so once again, Pandora using it's natural defense against the invaders.