"He showed that the "rating" worshipped by a lot of people, is totally useless is predicting who is the strongest!"
You can't say that ratings are totally useless because the rating favourite doesn't win every tournament. Only Aronian was clearly higher rated than the other players, but when he had a comparatively bad event very little separated the others, and at the moment Anand is the highest rated of them.
"Now, is it possible that In the eternal debate about who is the best player of all times, we can substitute Karpov or Kasparov with Anand?"
If you become the best player of all times by winning the latest tournament he is the greatest, otherwise he isn't.
I believe we should praise Anand, for becoming a candidate to the World Championship for the following reasons:
1. He showed that the "rating" worshipped by a lot of people, is totally useless is predicting who is the strongest! (Only exception is Carlsen!)
2. He showed that old players can be as strong as young one. Which should revise some federations beliefs on investing money ONLY on young players.
3. Differently from fake world champions like Botvinnik, or Karpov, which obtained their right to challenge the world champion over and over through politics and FIDE, Anand fought and won his right.
4. Now, is it possible that In the eternal debate about who is the best player of all times, we can substitute Karpov or Kasparov with Anand? (Obviously Fischer is the only one we can make a comparion to...)
I also like to point out that Anand should be praised for his influence on chess in India, to develop the game we love, in such huge nation, is something really great, and deserve to be remembered as an accomplishment for all human kind.