District 9 is fairly close to the premise of Alien Nation. Fairly close as in just shy of out-and-out plagarism. But that's OK. Nothing new under the SF sun.
Basically, a massive ship of alien refugees came to earth in the '80s -- and had the bad luck to land (or hover) in Johannesburg, South Africa. The aliens (now numbering about 2 million) have been herded into a refugee camp. Much tension between the shelfish-like aliens (called "prawns") and the locals. It seems humans can't fly the alien ship or use the alien weapons -- so they can't even trade their advanced tech. The aliens are being relocated to another camp further from the city. A clueless bureaucrat is in charge. Let's just say he finds the process transformative.
A fun movie that takes stuff we've seen before (power suits, alien refugees) and twists them around to make a fairly original statement about human rottenness and redemption.