Suicide is selfish, and it's not selfish. Choosing to live is selfish, and it's not selfish.
Any of the above can be true or false depending on how you define and measure "selfish" as opposed to "selfless" actions.
A person who kills themselves could be seen as selfless, even heroic, in a situation where more harm would result from their living. The religious concept of "laying down your life for your brother" is saying suicide is the ultimate good if the benefit to another is great enough, yet these phony religious ideologues are always the first to the guilt party, and worse, the ones most likely to conceal the act as a shameful thing.
Basically, the common way the term selfishness is used with suicide just refers to the loss and grief other people would experience with your suicide. That just means they're the ones being selfish if you think about it in wanting you to live against your choice for their own peace of mind.
So, any negative value judgements are nothing more than fabricated guilt and probably not worth worrying about imo. You can just as easily argue, or more easily argue, that suicide is selfless. It only has the meaning someone gives it, or accepts it as having.