As a Christian, I have to answer that the point is to live for God and spread the good news of Jesus. However, as I also have been and still sometimes am suicidally depressed myself, I can't truthfully tell you that that's the answer that's worked for me.
The way I see it, God gives us an earthly life. He doesn't just whisk us up and away to Heaven as soon as we accept Christ. He must want us here for a while first.
Christians are supposed to life for God, sure, but we are also supposed to rejoice. I think—and I still struggle with these thoughts—that we literally are here to take joy from this life. Within the boundaries of God, but, I think our happiness is probably actually important.
I can't back that up. I have only thought of it recently. I think about these things a lot, what with being suicidally depressed and all.
I think that we are supposed to endure the pain of this life for the sake of the joy in it. Even the most horrible of lives can have moments of joy. I think that those moments are meant to outweigh any strife involved in getting to them.
I don't know if that helps at all. I really don't. I'm not even sure yet if it'll help me. I just felt like I should share it, so I did.
That said, I can empathize with the "what is the point, anyway" kind of suicidal that you seem to be talking about. I'm so sorry that anyone else has to feel anything like what I have.