Attack is superior to defence in chess (because it's more dangerous for your opponent). I wouldn't describe Karpov's style as defensive, but he was a good defender when needed.
Your % of winning games depends much more on the level of your opposition.
Attacking your opponent is a very strong strategy at amateur level, but becomes more difficult to implement when you go up the ranks...
MOST winning games, are they usually won by being aggressive? I think I heard that Karpov, Lasker and Petrosian were great defensive players, they sat back and waited for opponents to make mistakes, THEN came on and beat opponents. But is that the best way to play? Can you play defense for 80% of a game, THEN go on the attack? or is it better to come out swinging, once you're well developed?
2nd question - If aggression pays, what % of a winning game is aggression? 80% ? 90% ? 60% ? I know sometimes you have to play a little defense to shut off opponent's attack, so that you can go back to YOUR attack, so how much of a winning game is aggression? What say ye?
edit: I included Pertosian and Lasker to the great defensive list.