Why are genetically modified foods good?
Because they are usually more resistant to pests and have greater production rates. Not to mention in some researches they are planning to use to produce medicines.
Plants are genetically modified aiming to obtain variations that produce more than the wild ones. This can be done in quantity, e.g. weight, faster, e.g. diminishing the maturity time of trees. Further, in some case they are using them to produce vitamins not present, such as bananas with C vitamins, or even medicines, such as fruits that produce insulin.
The plant productivity can be enhanced by:
Making the plants more resistant to pests, such as caterpillars and grasshoppers;
Increasing their resistance to harsh environments, e.g. plants to desert.
Increasing the weight and size of fruits and grains, e.g bigger tomato.
Nonetheless, there are several problematic, such as risk of contamination.