What science fiction does best—and I mean real, aliens-and-alternate-timelines, spaceship-y sorts of science fiction here—is unsettle us, the viewers. Not because of how terrifying everything is (although let's never forget that moment of abject horror in Alien when the alien bursts out of Kane's chest and leaves everyone screaming): that kind of unsettledness is a given.
No: when science fiction is doing its job, it leaves us feeling uneasy not about the world it creates, but about our own world—and ourselves. Sci-fi is by nature about what could be, about things that might plausibly happen, given a little bit of time and maybe a wrong turn or two in the lab. It looks at the consequences of scientific innovations, and it makes us ask basic questions about identity, institutions, societal structures, desire, morality, and ethics.
From Star Trek to Alien to 2001: A Space Odyssey and WALL-E, science fiction always works best by taking the familiar (people, places, relationships) and putting it in the unfamiliar (outer space, other planets, the future). Thus defamiliarized, we silence our reflexive reactions to ethical dilemmas and prejudices just long enough to let them sneak past our defenses like (forgive me) so many shape-shifters and make us realize that we're empathizing with a morally reprehensible action or character.
So the only real problem with Oblivion—which is a perfectly adequate, shiny Tom Cruise-driven futuristic action flick—is that it never asks us to be unsettled. In fact, it seems calculated to make us feel comfortable. How much you care about that may be worth considering. But you'll get your twelve bucks worth.
Sixty years from now, the planet has been gutted, the moon smashed, and the war lost. The humans have left the planet for the Tet, a big tetrahedronical space station orbiting the earth, and a colony on the planet Titan. The planet itself is now in the hands of a bunch of alien Scavengers, referred to in the film as "Scavs."
Just a couple humans remain—Jack (Cruise) and Victoria (Andrea Riseborough), who live together in a fancy sleek luxury pod, complete with its own pool (great for picturesque nighttime skinny-dipping). It towers high above the devastated landscape, which, we discover, is actually the ruins of Manhattan, the tallest skyscrapers still sticking through the dust (though, of course—contrary to reason but in perfect accordance with movie logic—a broken fragment of the Statue of Liberty pops up as well).
Victoria takes care of operations while Jack flies his nifty spaceship around and keeps track of the drones, part of a plan to extract resources for the other humans. It's a good life.
Victoria and Jack had their memories wiped as a security procedure before coming to earth. They live happily, not missing home, their only link to the Tet a little screen on which their boss Sally at mission control (Melissa Leo) appears every day to ask them if they're being an effective team.