His decision was NOT for the good of Ellie though. It's also why I think their relationship has deteriorated over the years.
Ellie isn't his daughter. She's a person who makes HIM feel a little better after the fact he lost his daughter.
It's evil because he gives a shit more about how HE feels more so than Ellie herself.
That lie is protecting himself because he knows it was bullshit and it's against what Ellie wanted.
First off how do we know his decision was not good for Ellie. All we know is that she could either be A) dead or B) whatever happens in the coming game. It is hard to argue someone is worse off then dead (though I get it is possible).
Secondly, Joel makes Ellie feel good too. She cared about Joel and wanted to be with him.
Third, we have no idea what Joel is actually thinking. I'm guessing in his mind he is doing this for Ellie and not for himself. Even if it is obvious he is doing it for himself too.
Forth, Joel didn't know Ellie wanted to die at that point.
Fifth, just because a 14 year old wants to die, do we let them?