Part 14: dotchan talks about the fall of the Greek pantheon.
OK, here's a query for you dudes boned up on the classics - when did belief in the Greek panthenon cease? Was it around the same time the Roman Empire adopted Christianity?
I don't remember the exact date off the top of my head, just look it up on Wikipedia or something, but belief in the pantheon was already eroding well before then (Socrates famously got in trouble for asking the wrong questions about the gods, but in my opinion his death was more politically motivated). We don't really have a lot of hard data on what people actually believed with regard to mythology--a lot of the stories were, as pointed out earlier in the thread, effectively fanfiction written by people who didn't necessarily think of them as fact. My guess is that the average person of any era was at least thinking "there's god(s) that need appeasing; just point me to the right temple(s) and I'll make my sacrifice(s)", but if you asked them they would only be able to tell you the broad strokes about any particular god(s). Worship of the Greco-Roman gods stuck around because they helped contribute to societal stability: the stories taught morals that upheld ideal behavior (though of course quite a lot of philosophers grew dissatisfied with asshole behavior and explored other religions once they came in contact with them), the regularity of rites appealed to the human need to belong to something bigger than themselves, and it helped people deal with the unpredictability of life.
And the statues were nice.