Yes, it is selfish in that regard, but don't start stigmatising suicides because of it.
An individual is most certainly not weak if they are considering suicide. As I said, its a completely normal response to abnormal situations whereby coping mechanisms have failed or the person has nothing left to cling to as a crutch. It could happen to anyone, so stop being so elitist. Some of the strongest people I know are those who you think are weak and they're strong for reasons you cannot possibly comprehend.
Suicide is about as selfish as euthanasia. It's akin to a victim of torture finally giving in and begging for their right to die to end the misery. The only difference being, the torture is all psychological.