According to this German site, Bobby Fischer has the record: 2787, with Garry Kasparov #2 at 2759, Anatoly Karpov #3 with 2722, Mikhail Tal in fourth at 2700 and Viswanathan Anand and Vladimir Kramnik are tied for fifth-sixth at 2699. I'm not sure what their method is and am sure that Ken Regan would disagree with it, but it's at least an entertaining list.
Many, probably most of us do believe that there has been some rating inflation, but even so it's hard to believe that even the Viktor Korchnoi of the late 1970s was stronger - measurably stronger, at that! - than Magnus Carlsen. Korchnoi's peak rating was 2695, while Carlsen is 2835, and our understanding of the game has developed since then. (Even Korchnoi now must know a lot more than he did then, even if at the age of 81 he can longer play with the same strength and endurance that he used to.)