Ahh, the infamous ME3 endings... yes, they were written up solely by the head writer(Mac Walters) and the project lead(Casey Hudson).
Their artistic vision, see, not that of any of the other writers. As one of them put it:
gamesthirst.com/2012/03/22/mass-effect-3-writer-distance-himself-from-game-ending-blames-casey-hudson/“I have nothing to do with the ending beyond a) having argued successfully a long time ago that we needed a chance to say goodbye to our squad, b ) having argued successfully that Cortez shouldn’t automatically die in that shuttle crash, and c) having written Tali’s goodbye bit, as well as a couple of the holo-goodbyes for people I wrote (Mordin, Kasumi, Jack, etc).
No other writer did, either, except for our lead. This was entirely the work of our lead and Casey himself, sitting in a room and going through draft after draft.
And honestly, it kind of shows.
Every other mission in the game had to be held up to the rest of the writing team, and the writing team then picked it apart and made suggestions and pointed out the parts that made no sense. This mission? Casey and our lead deciding that they didn’t need to be peer-reviewe.d
And again, it shows."
Casey is really smart and really analytical. And the problem is that when he’s not checked, he will assume that other people are like him, and will really appreciate an almost completely unemotional intellectual ending. I didn’t hate it, but I didn’t love it.
There's also an extra ending via DLC which might seem to give one a kind of hope after all, until it was confirmed on Twitter that the next generation just picked one of the first three, if you know what I mean.