Selfish people are the most successful because they acknowledge their needs. They also know what they want to do & be in life. They aren't afraid of getting &/or going after what they want. They know that they are the best & aim to get the best that life has to offer. They realize that if they don't respect, love, & cherish themselves, NO ONE ELSE WILL. They are of the school that charity begins at home.
Selfish people are also strong people who establish & respect boundaries. They refuse to be taken advantage of. They know that it is quite normative to place their needs, wants, & desires first & foremost. They are definite people who aren't afraid to know themselves. Knowing oneself is an imperative to achieving success. They also have a healthy admiration & respect for power. They know that power is a prerequisite in their lives & if they are going to achieve success, they must have a sense of their own power.
Selfless people, on the other hand, are the least successful in that they put others before themselves. That isn't normal but is a form of mental illness. No normal or intelligent person would put others' needs before their own. That is antithesis of the human instinct. Because they put others' needs before their own, they are open to exploitation by others. They are the type of people who let others take credit for their work or other tasks they undertake.
They really don't respect themselves so others aren't going to respect them either. They are seen as followers because they don't have what it takes to be a leader. They are furthermore viewed as quite powerless. They refuse to let their light shine, oftentimes diminishing themselves in favor of others. They aren't successful because they have little to no sense of self. They are also uncomfortable with power, seeing it as evil. They are unclear as to who they are as a result of putting others first. They are also unsure, even hesitant as to what their particular desires are. They may even subvert their desires, wants, & goals are selfish. These things are not conducive to success. They are self-loathing, self-denying, even self-abnegating which borders on the abnormal.