To understand the reason why the path of 'Good' is the best one to take, one must agree to two fundamental postulates of life:
1. The purpose of life is to achieve eternal bliss. Throughout life, a person tries to do things that lead to a sense of happiness. People like to have fun. It is this essential desire to be truly happy that keeps us alive.
2. The world is ever-changing. Our bodies, our souls, all of our possessions, all of our emotions are subject to the whims of forces beyond our control (Gods). Nothing we do will remain as it is, for with time, everything must erode.

If you believe these two postulates, listen to why the path of good leads one to live a better life.
First let us take the case of an entity who follows evil. Now, I do not presume to understand all about evil, but it is generally held that evil people have little feeling for others. Their motives are always dark, mysterious, that lead to the betterment of themselves to benefit their rank in society. A so called 'Survival of fittest' is what they try to live by and achieve, and in order to survive, they feel they must become more powerful.
All these means, all of these ends, are in their nature essentially selfish. True, all things that give selfish pleasure breed an illusion of happiness. An evil character will smile with glee as he smashes the head of his poor foe to the ground. However if one psychoanalyses the mind of any selfish man, you will see that he is not happy at all. His happiness is a false one, more temporary than other's.
From continuous 'thinking' about objects and selfish desires, one forms an 'attachment' to them. From these 'attachments' arises a 'longing' to guard those benefits from anyone who could take them away. From 'longing' comes 'anger' as the object disappears, as all things must, and the fiery temperance controls one's self. From 'anger' comes 'delusion', and the intermittent verdict that everyone is part of some grand conspiracy against you. From 'delusion' comes a 'loss of memory', of what people and surroundings were like before this great catastrophe. From a 'loss of memory' comes the 'ruin of discrimination', whereby one cannot tell between what is inherently right and wrong, or food from fire, or water from poison. From 'ruin of discrimination' he 'perishes', into nothingness...
This tragedy befalls many whose motives are egotistical-- many of those who are evil, or turn to evil.
As one lives though the many stages of life, one gains a certain affinity for the actions one does. If I take a bite of a lemon, I will realize that this lemon has a stark sour taste that repels my tongue. I will not eat lemon again. For every action we do, we gain such an affinity. But these affinities lead to prejudice, for those actions WE prefer and against those WE detest. The important word in that last sentence is WE. Affinities are selfish by their nature. True, one cannot escape having these affinities, but once can limit their influence by creating selfless ones. I help a newbie, and gain an affinity: it pleases me to see a protege grow into an image of what I wanted to become. Even though this action pleases ME, it is more selfless in its nature that it benefits others, in addition to myself.
These kinds of affinities lead to a happiness in seeing benefits put upon others. This type of happiness is a truer one, more permanent than the false satisfaction gained through evil. It will not cause any attachment to be placed upon objects, for these objects are themselves intangible. Selflessness will never make you angry, never cause delusion, or a ruin of discrimination. Selflessness will never cause perish. Selfishness is the essense of Good. And though Good, one can become eternally happy.

Penned by my hand on the 18th of Mayan, in the year 271 AF.