A few years ago I played on a world champion online FPS team and we put in crazy hours for that. It took us two years to hit the top and during that time we probably averaged 12 hours a day, but it was a video game. If I played any less than that, it was noticeable. For me its apples to oranges, because although I love cycling, I have to do things I don't really want to do to be good at it (cycling on a trainer, in the rain, sub 50 degree temps, etc). That isn't even counting the nights I go to sleep hungry (although fatties seem to have no issue winning crits).
Some people can get on their bikes and do well, especially if they are athletically gifted or coming from another sport. If someone who just got off the couch asked me what they needed to do to win a Cat 5 race, it would be a pretty tall order. Cycle 10-20 hours a week, $3,000 on equipment, lose weight, group rides at least once a week, and call me after you hit 10,000 miles.