Over the last century, nutritional science has evolved by leaps and bounds. Whole new 
classes of nutrients have be identifies. In fact, we have been blessed with astounding nutrient rich foods which we are still discovering. A nutritional scientist name Dr. Joel Fuhrman managed to develop a scoring system for nutrient density, which he then named the Aggregate Nutrient Density Index or A.N.D.I for short. The ANDI system ranks the value of food on a basis of nutrient per calorie. He found that the higher the nutrients per calorie the more effective the diet was at improving quality of life.
The ANDI rankings only take into account the essential nutrients and anti-oxidants that are measurable. With the discovery of new nutrients some foods have not yet been factored in to the ANDI scale. Due to the speed at which our understanding of nutritional benefits is growing other factors besides the ANDI score need to be taken into account in order to construct the most nutritionally beneficial diet.
These other factors are:
1) Levels of micronutrients per calorie (vitamins, minerals, phytochemicals)
2) Amounts of macronutrients to meet individual needs (fats, carbohydrates, proteins)
3) Avoidance of potentially toxic as well as other harmful substances (trans fats, sodium)
The trick to constructing the most filling and nutritionally beneficial diet is to meld the ANDI rankings and other factors together into a system that works for you. Leafy green 
vegetables such as kale, turnip greens, collard greens, and watercress are a good base to start with due to their perfect ranking of 1000 on the ANDI scale. Other options such as spinach, carrots, broccoli, Brussel sprouts, and cauliflower have high ranking scores and should be utilized as well.
A healthy diet requires a wealth of phytonutrients and anti-oxidants. Our body should, ideally, have a reserve of these agents in order to effectively deal with the damaging impact of metabolic waste. In order to insure these reserves are available it is important to eat plenty of foods rich in nutrients. Healthy fats are also essential in order to maintain energy levels so our body can function. Calorie rich foods with healthy fat sources include avocados, grass-fed meats, free-range eggs, and nuts/seeds. By combining all these tips you should be able to construct an amazing nutrient rich diet that will improve your quality of life.