I think it's impossible to compare golfers from different ages, obviously because of technology, but also because of competition and the style of courses. There are a handful of greats, and any one of them could be argued to be the best. For all we know, Bobby Jones might have been the best ever. If I remember correctly, he retired at around the age of 29 to do other things besides golf, but while he played he dominated everyone. Had he played into his 50s, he might have set major records that Jack couldn't have touched.
People don't talk about him as much though because he retired so young and didn't set any real career records because of it.
I do think Tiger will shatter Jack's major mark. I expect he'll win around 25 before he retires, and he will likely throw in some 2nd places as well.
Edited to add: At this moment, Tiger has 13 major titles and 4 second place finishes at the age of 32. His 1st and 2nd place finishes have occurred over a period of 11 years, starting in 1997.
Jack had 18 major titles and I counted 19 second place finishes. Those 1st and 2nd place finishes occurred over a period of 27 seasons.
Jack's last major title (1986 Masters) came at the age of 46. Tiger has 15 more seasons (including this one) to play before he turns 47.
One other advantage Tiger has are the health and nutrition advances today. He'll probably be able to play well enough to compete for major titles into his 50s with the way he handles his body.