By just reading the title of the thread and butting in; I think that suicide is a bit of both, both ways. 
Suicide is tragic not only in the way that someone loved dies, and that the person wont come back. Its tragic in the way that the suicide victim was pushed to a point where he/she saw no other options than to end his/her life. It also ties to the second part, selfishness. 

Every case is different, and usually(What i think at least) when someone is driven to take their own life, the thought of it being selfish isn't even on the persons mind. AND i think that, if someone has suicidal tendensies, although not always noticable, an aditional reason for the person to FEEL so suicidal is because everyone around him/her has turned a blind eye to the person reaching out, OR seemed too selfish to notice (definitely not all of the cases here). 

Point is; I think that both selfishness and tragedy are a cause AND an effect of a suicide.