Gave them a mention on the other thread but you can forget these 1 event wonders as to be a true "Sportsperson" you have to be good and more than 1 thing therefore my vote/s go to
Daley Thompson for the Decathlon
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Jessica Ennis for the Pentathlon
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Both of these events require competitors to be good all rounders at a lot of different events, it's actually like going back to the original "True" Olympic spirit etc
End of thread

…Or simply Jacks of all trades, masters of none?

Just playing Devil’s Advocate, I have huge admiration for both.
Personally, I’d say one of the criteria would be to maximise the talent you have and to overachieve based on that level of talent. Thus someone like Ronnie O’Sullivan would be second to Stephen Henry, despite the Rocket being more naturally gifted. Ditto for the likes of George Best. Both are head and shoulders above their peers in terms of pure talent but neither translated that into the level of success their talent deserved.
It’s difficult enough to pick one from each sport, never mind an overall winner:
Motor cycling: Hailwood, Joey Dunlop, McGuinness
Motor racing: Moss, Clark, Stewart
Athletics: Daley Thompson, Jess Ennis (told you so, BR!), Coe, Cram
Cricket: Botham, Boycott (to illustrate my point!)
Tennis: Murray
Boxing: Lewis
Football & Rugby I feel are too partisan for objective discussion.
All of whom competed in my lifetime and thus ignore the greats of the past whose exploits weren’t captured on film and who therefore are at a disadvantage in a discussion like this.