If you really think that, let me ask you something.
Do you know what it's like to think about killing yourself everytime you see a window, rope, or gun? To be afraid that everyone else hates you and that no one will ever love you? To cry all the time over little things because that's all it takes to push you off the edge? To be afraid of killing someone else? It feels like a living hell when you don't even like your own mind. And I'll probably get called Emo for this but I don't give a crap. I wanted to kill myself at the age of 10, and if that's screwed up to me.
Depression and Anxiety are disorders and should be treated as such. And while I do agree with the fact that Suicide doesn't make it better, and that it hurts others too, saying that someone is selfish for feeling suicidal isn't going to help.
Only if they don't ask for help, but if the others do not want to help or think that his / her problem is bullshit (which is temporary, which is joke, etc) then this would not be part of the selfishness from the person who wants to suicide.