Avatar certainly looks good, and the technology is going to be groundbreaking. But what makes district 9 so good is the doco style and the fact they didnt set this in Manhatten or somewhere lame like that. It's alot more believable baing set in the slums of South Africa.
I guess the only unanswered question i had was why was the fluid that propells their ships/technology, responsible for transforming humans into aliens? Seemed like that really didn't get properly explained, even though it was a fuckin cool plot line. i guess because it was based on their DNA or something, must have made humans mutate.