I put very little stock in this because drivers of previous eras had far fewer opportunities. In the '50s and '60s there were only 9-10 races per year. How many might Fangio or Clark have won with twice the number of races? And those years MS totally dominated would not have produced all those wins if there were only half as many races. I think winning percentage is more valid.
In which case Vettel has the advantage of running in an era of 'bullet proof reliability'
I think the best measure is teammate comparisson (of course, this too is muddied by eras with different numbers of teammates, and different scoring systems)
Perhaps pole position percentage is the truest measure of a 'great' driver? That one lap mastery of machine is seldom affected by reliability, scoring system, or teammates. Are there any drivers who have a disproportionate ratio of poles to wins? (Besides 2012 Hamilton
)