Schumacher matched Juan Manuel Fangio's record of five world championships with victory in the French Grand Prix on Sunday.

That prompted Scheckter to elevate Schumacher above the sport's greats, even though he says the German is not driving in an era of intense competition.

"I had reservations in that he did not have an Alain Prost or Ayrton Senna to run against him most of the time," Scheckter told BBC Radio Five Live.

"If you look at his record, not only is it five times but he missed out by a little bit on a couple of other occasions, like when he broke his leg (in 1999), so it could have been eight times.

"It doesn't mean much comparing one era with another but if you look at his record, for what it's worth, he's the best of all time."

But Scheckter warned that having achieved so much success, Schumacher will find any drop in form hard to cope with.

"He hasn't been beaten and when he is he will feel the pain even more," said the South African.

"Most champions give up very soon after they get beaten regularly."