Difficult to say about the result..Fischer was very "thirsty" to reach the top,but i am almost sure that he wouldn't play so passionate to defend his title.I believe he would probably lost from the ambitious young Karpov.Same scenario when Capablanca smashed Lasker but he couldn't defend his title against Aliekhin (i compare him with Karpov-both ambitious and very very well prepared for the match...)
Sometimes will wins knoledge..
Anyway if you want to see games and learn about Fischer (then you could make better decisions!) check this group dedicated ti him:
http://www.chess.com/groups/home/bobby-fischers-group
For me this had the potential to be an epic match. Bobby Fischer, the man who took on and broke the Soviet dominance of the game; and Anatoly Karpov, the young Russian who catapulted up the world rankings in a short space of time to get his shot of the title.
As is well known, Fischer was very particular about match and tournament conditions (remember Souse 1967), so it never looked likely that the match would take place.
But let's suppose the match did go ahead with let's say a best of 24 games and the benefit of the draw with the champion. Who do you think would have won? Could there even have been a match between Fischer and Kasparov?
All views welcome