Mauger would have to be my number one choice, purely on his professionalism, Racing record and Wordl Championships.
Fundin would, on records alone be second on the list - I never saw him ride.
Briggo, my personal favourite, would be third (I would like to have put him first), but you cannot overlook the achievements of those above him.
Rickardsson would be fourth - again on his World Championship record.
Olsen last. Never my favourite Rider, in fact he was one of the ones I liked least. I can't deny he was a very fine Rider though certainly, to my mind, not in the very top class of Riders like the ones above him.
Honourable mention for Erik Gundersen who I personally rated higher than Olsen.