I'm sure someone else has also answered this correctly. The obvious answer is Carlsen. Because of the actual question, "who's" better. Not who "was" better. If the question was who was better in the 1990s, it was Kasparov. If the question was who was better in the 1960s, it was Fischer. Anyone can be better, depending on all sorts of factors and circumstances.
But the greatest of all time, Fischer.
Fischer wasn't the greatest during the 1960's, that was Smyslov, Petrosian, Keres, Spassky and Tal. Fischer and Karpov were the best during the 1970's.
OK, 70s. Same thing. The point isn't at which particular time, the point is it was in the past. The question was who is presently the best. So that would be Carlsen.
I'm sure someone else has also answered this correctly. The obvious answer is Carlsen. Because of the actual question, "who's" better. Not who "was" better. If the question was who was better in the 1990s, it was Kasparov. If the question was who was better in the 1960s, it was Fischer. Anyone can be better, depending on all sorts of factors and circumstances.
But the greatest of all time, Fischer.
Fischer wasn't the greatest during the 1960's, that was Smyslov, Petrosian, Keres, Spassky and Tal. Fischer and Karpov were the best during the 1970's.