Apologies for my lack of reply or comment.
Here goes; it is impossible to compare drivers of different eras, different rules and point scoring systems. All I can try and do is list who I consider to be the greatest in any particular decade.
1950's Ascari, Fangio and Farina.
1960's Clark, Surtees and Brabham
1970's Stewart, Lauda and Peterson
1980's Villenueve (G), Prost and Mansell
1990's Berger, Senna and Hakkinen
2000's Alonso, Montoya and Hamilton
2010's (so far) Vettell, Alonso and Hulkenberg (the last named will surely be a great if a top team sign him!)
I am unable to include Schumacher for his flagrant disregard of a black flag in 1994, and his subsequent deliberate elimination of Damon Hill in the 1994 Australian Grand Prix. I had given him the benefit of the doubt as to whether it was deliberate until the European Grand Prix of 1997 when he tried the same trick on Jacques Villeneuve.
Fortunately after that the governing body half saw sense and punished him, though not nearly severely enough in my opinion.
That's my opinion anyway.
Kind regards
Martin