Today: There's Tiger, then a pretty substantial drop-off to Phil, then another pretty substantial drop-off to everyone else.
Back Then: There was Jack, then a slight drop-off to Hall of Famers like Palmer, Player, Irwin, Watson, Trevino, Floyd, Casper, Middlecoff, Miller, Jacklin, Ballesteros, etc. You can probably think of a few more. Nevertheless, can you name eleven players today at that level? Not to mention Jack's later years included Crenshaw, Norman, Kite, Couples, Stewart, Azinger, Sutton, Faldo, etc.
In my mind, Tiger is extraordinarily talented and an argument can be made that he is the best of all time. However, given Jack's success against these great players (18 wins in Majors and 19 seconds!) I believe that Jack is the "Greatest". Tiger will likely beat Jack's record but I'd say that in doing so he hasn't accomplished as much.
[This message has been edited by weeza (edited 6/28/2008 3:24a).]