James Cameron's Avatar: The Game is a prequel to the recently released film. The story revolves around the planet Pandora, a lush green world that is home to a toxic atmosphere, a number of hostile plant and animal species, and the tribal race of blue-skinned natives known as Na'vi. You play as Ryder, a soldier of your own customization who has been selected for participation in the RDA's Avatar program. This program was conceived as a means of communication with the Na'vi, who aren't exactly fans of humanity. By slipping into a machine, Ryder can transfer his/her consciousness into a genetically-engineered Na'vi clone known as an Avatar. A few hours into the game, a war erupts between the RDA and the Na'vi, and Ryder is forced to choose a side. Naturally, this means you've got two fundamentally different campaigns to play through. This is the developer's way of trying to give the game some longevity, but it doesn't quite succeed all the way for three main reasons. First, the storytelling flat-out sucks; you won't become attached to any of the main players, and by extension, you won't care what happens to them. Second, there is apparently no such thing as moral neutrality on Pandora. This makes the whole experience come across as preachy; the Na'vi are very clearly the victims/heroes and the RDA's work is shown as little more than village-razing and planet-raping (though their actual mission is for an apparently priceless natural resource). The final reason is that, well, the game isn't terribly fun to play.
Regardless of which faction you choose to fight for, Avatar: The Game is a pseudo-open world action game. I say "pseudo" because you can't literally go anywhere. The jungles of Pandora are scored with conveniently cleared-out areas (probably due to the RDA's less-than-honorable work). The beaten path is the only path, and those who want to explore their own way will be disappointed. Furthermore, if you want to move faster, you'll need to use a vehicle. The vehicles are a huge pain in the ass, and what's worse is that some missions require you to use them.
When you're not turning RDA soldiers into pincushions (or gunning down Na'vi), you can play Conquest, an optional strategy mini-game that doesn't really offer that much incentive to play. It plays out like a board game that would require a lot of number-crunching. It's interesting in and of itself, but it doesn't figure into the gameplay heavily enough to help the entire package stand on its two feet.
Structurally, Avatar: The Game is remarkably similar, if not identical, to most other open world games. You traverse the jungles of Pandora, accepting and completing quests, all of which require you to complete a number of uninspired objectives. If you've played an open world game before, you've completed missions that are borderline identical to those in Avatar: The Game.