Okay, it starts with same deal as Independence Day and War of the Worlds. Menacing ships hover above the city, panic ensues. Now Randy Quaid flew his plane into the laser port of the mother ships in ID4,and both human germs and rocket fire beat the tripods in WoTW. 'Cept this time, in Skyline, these things don't get damaged by our weapons. We all cheered when the UAV drone survived the gauntlet and fired the low-yield nuke into the ship. It wobbles and crashes, YAY!!! But then - and this was a painful moment - the dam thing reassembles itself with nano technology... NO!! The ships don't register damage from missiles; even the biological meat-slab monsters survive point-blank RPGs, and when a heroic F-22 pours cannon fire into one, gets waxed, and crashes into the burger being, IT STILL DOESN'T DIE!!!! Well, let's allow the propane to fill the room, light a match to vape the place and take yourself along with it - sorry NO EFFECT!! None of the main characters get it easy, except for the pregnant woman at the end who is "spared". Skyline takes a "realistic" approach to how an invasion by extraterrestrials would actually pan out in terms of there being no contest.
Skyline takes us into the motive of the aliens, something which not too many other alien invasion movies do. Yeah, we are usually told or it's hinted at, but never shown. The jarring sight of seeing ... ewww... brains and spinal cords removed and implanted into the dormant burger beings - - so THATS why they're here... Remember the scenes in The Animatrix with the machines using catatonic humans as guinea pigs. After years of seeing the humans prevail against the aliens, this time NOTHING works. Heck 2009 and 2010 have seen that theme played out - human paramilitary guys get wiped out by the Navi in Avatar, and the prawns in District 9 kind of beat the police at the end.
For my tastes, Skyline wouldn't have been any better if the "beautiful party people/melodrama and infidelity" first act was absent or changed. I would have liked to see us get to actually know and care about the characters, but that wouldn't have changed the idea of "nothing can stop the aliens; no, sorry moviegoers, we don't win this time." A pretty good spin on the usual "Humanity triumphs" ending.