It is not selfish, at all.
Saying it is selfish, solely basing on what the aftermath will be, is absurd, for the person is completely an individual from its moment of birth. What ties us to others are only two things: our physical condition, for we are bound to this world as fleshly beings, organic creations which have to reproduce and perish sooner or later; and, deriving from the previous reason, whatever symbolisations we may acquire through language, due to language being the platform on which humans build relationships, ergo, society. Therefore, considering suicide as a selfish act contemplates a sort of treason towards the fellow humans, the closest ones, only because of there being an abstract bond between them and the suiciding individual. Even if this fundament, the bond, is certainly valid for us language-defined existences, it is rendered meaningless once one encounters oneself as a completely independent, conscious being, that will only fade if his predisposed needs are not satisfied.
We are dependant only as much as we are organic and social, yet we, as individuals, are completely free once language loses its meaning and flesh passes away.
On a more culturally apprehensible note, suicide is in no manner a coward's way out. You need as many balls to commit suicide as you need to live in this universe, given that there is no such thing as Rinnne-Tensei or some unholy Reanimation Jutsu.