It just occurred to me that Ryan Hall's 4:17 mile is a nice demonstration that the different events in distance running are, in fact, different events. It's nice to know that we're not swimming, where if you're world-class in one event you're basically guaranteed to be world-class in a few others. Here, Hall ran one of the all-time great marathons by an American, yet his mile time falls short of what would be considered "elite" for high schoolers.
(And yes, the marathon to the mile is admittedly the extreme, so there's much less difference between, say, the 5k and 10k, but still ....)