I used to have this conversation with my Dad. My Mum died when I was 3. (Natural causes- cancer- not suicide.) Naturally, I missed her. I suppose as a way to try and get me to move beyond it, my Dad would tell me that, right at the end, she was really suffering and, it wouldn't be fair to wish her back in that condition. Kind of a weird thing to say though really- it's not like resurrection on this earth is even possible! so- why then insist it would only be possible under those conditions?
But anyhow- as a concept- surely, we wouldn't wish a mere existence of suffering back on someone we loved. We'd prefer them back in a happier state. I imagine that's what you would wish for your friend. That they'd return to live a happier version of their life with you. That isn't selfish. That's hoping you'd both benefit from it.
I suppose you have to consider whether that would be realistic though. I'm not sure if they took their own life but in a way, I suppose that further complicates things. Someone who goes via their own hand I imagine would probably want that decision respected.
As to whether it's selfish- maybe that depends on whether you would actually do it (if you could that is.) Thinking about it is one thing- it's natural to miss the people we loved. It's natural to want them in our lives still. To actually do it though- if you knew they were coming back to the same problems. Not sure. That's a bit murkier to my mind. Would you though- realistically? (If you could.)