Hmm, a very interesting question to bring up! I do believe each World Champion is great in their own way, and each had their own different approach to taking the title. It’s also very difficult to judge drivers from different eras (as was the case when the Champion of Champions contest came about), but here are a few suggestions:
Farina: Beat Fangio in the very first season, where a single retirement could heavily impact the championship standings. Farina won by just 3 points, gifted from a fourth place. The Alfa-Romeo won every race in 1950 (excl. the Indy 500)
Hawthorn: Won the Championship with just 1 race win in 1958. He was also given the title after fellow Brit and rival Stirling Moss appealed Hawthorn’s disqualification from the final race.
P. Hill: Was given the title in tragic circumstances, after his team leader was killed. Least number of points for a Champion and tied for fewest wins. Ferrari dominated that season.
Andretti: Like Hill, was given the title after his teammate, the highly rated Ronnie Petersen, was killed. Lotus dominated that season.
Scheckter: Used consistency to beat the very popular Gilles Villeneuve in 1979 in a very strong Ferrari.
Mansell: Tried time and time again to win the title, lost out to Prost in ’86 despite having the best car, lost out to arch rival Piquet in ’87 after breaking his back, and was soundly beaten by Prost at Ferrari. Dominated in 1992 in that all-conquering Williams, retired, came back before a dismal move to McLaren.
Villeneuve: Gave the more experienced Damon Hill a run for his money in his debut season, and won many races in yet another very good Williams car. Never won a race after 1997, and now we just can’t seem to get rid of him.
Don’t get me wrong, what each of these achieved is something only 32 people ever have, but there is obviously the argument that some are greater than others.
Personally, I would say Villeneuve. Peaked far too early, and then just gave up after running out of things to crash into.