“Most things are relative aren’t they? Sounds like Peterfile was well above average at snowboarding, just not international level. Surely that still qualifies as good though?”
It depends on how high the standard was elsewhere. If the standard was poor in the UK and internationals are doing badly against any number of random Continentals, Americans etc, than being in the top 25% is no big deal surely. You cant really just look at a national level, the Saudi Arabian snowboard champion is likely to be pretty crap in absolute terms. The guy qualifying 90th for a world cup DH might usually be the best rider in the bike park but, he is crap when compared to the top 10. etc, etc.
So, I reckon to be good you need to be in the group above +2 Standard deviations from the global mean for whatever it is you do. Therefore, most people will never find anything they are really good at, above average maybe but that’s all.