The best of the bests of all times with no doubt is Hanno Prettner.
He competed in 8 T.O.C`s (Tournament of Champions) and won them all!
He competed in 7 F3A World Championships and again won them all.(In 1991 Chip won it - Hanno didn't compete that year)
His last WC was in '93 and he won,he didn't compete ever again.
He won the Worlds in 1983 with a plane called Calypso his own design and that plane was giving to Formula 1 legend Ayrton Senna from Brazil.
Besides that he won the European Championships 16 times.
He never lost a competition.
He retired undefeated.