Interesting discussion. One which can be never-ending and is no clear answer on in my opinion.
Yes, the competition in Jack his days is most probably much weaker then it is for Tiger nowadays. But if you would be able to put Jack in the present time, with better material, better proffesional guidance both in training as mentally he would probably be a better golfer then he was in his days. Would he win as much, that we can never know, because of the better competition also. Same goes for Tiger, put him in the 60's and his level of playing would probably be less (but maybe even win more?).
To me, they both dominated an era in the golfsport, they both were (and Tiger still is) very important for the sport and brought it to the next level. Very impressive.