"Variety is indeed the spice of life" cannot be more true when it comes to a nutritious diet. Eating a variety of food ensures that the body gets all the nutrients it needs.
The food pyramid divides foods into 5 broad groups –cereals/pulses, fruits/vegetables, dairy, fish/poultry/meat, nuts/seeds/fats/oils/sugar. It is important to consume all the food groups as well as maintain variety within the food groups.
No single food group can supply all the nutrients. Choosing a variety of foods within each group also ensures that you will get the variety of nutrients you need, besides making meals more interesting. Some vegetables and fruits are good sources of vitamin C (citrus) and vitamin A (papaya), while others are high in calcium (figs) or iron (water melon).
This means our search for the best fruits/vegetables/grains/oils/nuts are unwarranted. Rather, attempt to choose as many different foods, which may be more interesting and pleasurable.
In addition to nutrition, varying colors, flavors, textures, shapes, temperatures of meals and cuisines helps to make eating more interesting and enjoyable. Different ingredients from different cuisines strengthens the principle of variety and its benefits.