Been watching GP racing since 1954, although good Mansalls not anywhere near the best :

In my opinion the best ive seen are:

Fangio
Clark
Moss
Senna
Schumacher when on song.

My favourite was Clark simply the best by a margin.

As a British driver Mansall would be behind:
Clark
Moss
Stewart

Unfortunately few of you lads have been around long enough to make a judgement of whos best. GP racing started in 1950 so ive seen most of it.
Today its as bad as it gets & something must be done.
Rod