On the Beach, 1959 movie with Gregory Peck. Post apocalyptic sci-fi. Depressing as hell, and would be worth revisiting. Only problem is, they'd probably want to go away from the nuclear fall out angle (doesn't resonate as well these days), but that's sort of a key aspect to what's happening.
Them. The CGI would kick butt, and while the original is a 'classic', it's also very cheesy all around. However, the opening sequence is chilling, and I think if it was handled right, could be pretty good. With some people's current fears over GMO's (it's the attack of the killer tomatoes!), giant insects might be appealing. Then again, how about remaking Attack of the Killer Tomatoes!