Wow never looked at it that way, thanks. I guess you are right, diet is the basis for everything, while exercise is a supplementation. I think I forgot the meaning of the word diet and took it to mean eating in a specific way but actually no matter what you eat is your diet as you mention. And if you eat nothing you die, while if you don't exercise doesn't mean you are going to die. So yes looking at it that way diet is much more important.
I think the people who said exercise/diet were equally important, were looking at diet in smaller variations. Diet like being on a specific, strict diet. For example a diet with some grains vs. strict paleo diet.
Most people today "watch" to some extent what they eat. Not that it's very intelligent according to our standards. But most rational people restrict their intake of what they know is really bad, such as fast food. I don't know anyone who eats only McDonalds like the guy from the supersize me movie did. People know that fast food is unhealthy but they either don't know HOW unhealthy it really is or they just don't care.
About Michael Phelps I don't agree with you completely. It's easy for you to sit and condemn his diet and say that his health is terrible, but you haven't won olympic gold medals.
You just have a theory. Nobody has a guarantee for lifelong health, no matter how perfect their diet is.
And, the rate of cancer in people considered athletes is something like 1 in 7, while it in the general population is 1 in 3. It might be because athletes are more conscious about what they eat, but I also think exercise is a factor for good health. Obviously not many athletes today eat low carb/no grain.
If you put two people on the same diets, the one that exercises will be healthier and feel much better.
Sure Michael Phelps diet might not be perfect for health according to our standards, but he sure has made some results in his sport and is very physically fit - those things count for something too.
And Lance Armstrong supposedly cured himself of his cancers by exercising as much as he could.