You can read a hundred different "experts" and get a hundred different opinions on what the best food is. I'm not going to argue that but I do have my opinions. What I am going to do for the most part here is tell you what you shouldn't eat.
First and foremost, the bane of modern civilization, is soda. You get absolutely no nutrition, empty calories, and lots of chemicals and harmful acids. Even if you drink diet pop, you're still getting chemicals and acids. It's no good and if you care about your health, you shouldn't drink the stuff. It was hard for me to give up my beloved Mountain Dew but I did and feel much better for it.
Hydrogenated oils are another on the list shouldn't be consumed. It's not natural. It's created by adding hydrogen to vegetable oils. There have been many studies done indicating the harmful consequences of hydrogenated fat products. Do a search and find some if you're interested. One study I read even linked skin cancer to it's consumption. This particular study said sun exposure doesn't cause skin cancer unless one also consumes hydrogenated oils. People who get lots of sun but don't consume this product have very low rates of skin cancer. Bottom line is that it's no good and should be avoided.
Don't eat white. By this I mean white flour, white sugar, white rice, etc. They provide calories with very little nutrition. Eat whole grain products, brown rice, and use honey or maple syrup or raw sugar as a sweetener if you must. At least the raw sugar does provide some needed minerals which white sugar is lacking. Is a piece of birthday cake on your child's birthday going to kill you? No it won't but few and far between is best if you can't or won't do away with it all together.
High fructose corn syrup is another and it's in most sodas as well as lots of different processed foods from bread to ketchup to salad dressings to snack items. Read labels and avoid if you can. Once again, there are lots of studies done about this which you can find if you care to look.
Regardless of what else you eat, if you stay away from these things you can't help but improve your health. I think almost everyone would benefit by avoiding these and adding lots of fresh vegetables, particularly the green variety. A large salad a day would do wonders. Raw fruits, nuts, and seeds are other items most of us could stand to eat more of.
I don't think there's a one size fits all diet plan. One needs to be flexible regarding one's own individual needs, metabolism, genetics, health problems, etc. Some can eats lots of grains to good effect, others can't. Nevertheless, avoiding the bad and concentrating the bulk of one's calories on the good, you can't help but be better for it.
Remember, you are what you eat. Garbage in, you will get garbage out. It's that simple.