2. War of the Worlds (2005)
While Steven Spielberg's War of the Worlds was of course only an adaptation of a previous film as well as H.G. Wells' classic novel, it is probably the most famous and widely-consumed of the three, hence its place here. What's important, and what remains consistent through all three films, is its almost hilariously anti-climactic ending, in which all hope appears to be lost, with the aliens mounting an unstoppable strike against humanity, when suddenly, their shields begin to fail, and the aliens perish. Indeed, the martians could not withstand the bacteria present on Earth - due to Mars having none of it - and so the aliens just die, denying the viewer any sort of climax in which the military wreak havoc on the aliens with bombs and machine guns. It's a great ending, though, because it's so thoroughly ironic; rather than just flying in the face of audience expectation, it is really quite fiendishly clever. When it seems as if nothing can stop the outside entity from ruling over Earth, it is the aliens' own alien nature that is their downfall.