I think diet is about the only answer here.
I'm 6'4" and 196#.
I do intense runnning, weights, aerobics, 5x a week and that alone just doesn't work.
Started to cut out the bad food, still ocassionally, and i can finally see some definition in the abs, but still a ways to go.
My only purpose is to achieve it at one point in my life, as I can't see maintaining the kind of diet that's needed to keep your body fat so low. I'm at 12%.
I've looked at all of the 6-pack diets and just am not interested in following some strict regimen, but cutting out some of the fattier foods seems to be helping (might just take a while longer)