Last fall, a former teammate and friend of mine somehow got involved in a running/fitness discussion with his co-workers. His 1500 PR is 3:54, and he still trains hard. He bet them a total of $400 that they would not be able to beat him in the mile (well, actually a 1600) even if they teamed up and ran 400m each. If he won, he'd get $100 from each person. If he lost, he'd have to pay each of them $100. They were given up to a year of training time if they needed.
Four guys in the mid 20s - early 30s age group took him up on his offer. He worked in an engineering firm, so they all had sedentary jobs. None of them had any track or cross country experience.
They said they were "ready" last week, so he raced them after work on Friday and got dusted despite being in sub 4 1500 shape. He ended up losing by 20 seconds to the team, which ran a 3:56. Their splits were 58, 63, 55, and 60.
Now, I know that the sample size is small, but I think it's pretty clear that the average person runs a lot faster than what many people on here think. Granted, there was some self-selection going on (an obese guy wouldn't have taken that challenge), and some of them occasionally played recreational sports prior to last fall. But none of them had played any kind of competitive sport in college, all of them were self-coached, and their running form wasn't the greatest. One of them didn't even wear spikes.
Face it, distance runners are mainly rejects who couldn't hack it at other sports. If you trained a random group of ball players and a random group of distance runners equally, the former would beat the latter by a lot in any distance below an 800.