The Rejection Ending.
This could've been the great redemption of the Bioware writing team. Just make a simple ending. The main game and EC can keep all their other-ending-nonsense. The Reject ending would be where Shepard shows the kids' illogic through basic explanation and evidence (i.e. EDI becoming a person and waxing philosophical, Legion's individuality and humanity, peace between Geth and Quarians, the constant defeating of AI throughout Shepard's career, having the Crucible as an emergency measure, etc.) Say "we'll take our chances with our own synthetics." The kid, being a supreme being of massive intellect and understanding, realizes he doesn't want to hurt people, and, knowing their Cycle of Destruction solution "won't work anymore", by their own admission, simply, goes, away.
Or, crank up the awesome:
http://arkis.deviantart.com/art/Mass-Effect-3-Alternate-Endings-SPOILERS-289902125
To 11:
http://www.koobismo.com/
I should say something about the good Professor Drayfish, whose original articulate explanation (and current long, rambling ones) allowed many people to resonate with. I for one, see themes and endings as different things, and while it's good measure to resound the theme(s) at an ending, an ending, like any scene, can be about whatever the writer wants their ending to be about. Which to me, is what a theme is (Definition of a theme: what a story is about.) As per ME3's Catalyst reveal, it turns out the theme of survival vs. Space Gods is irrelevant, as the God of the Galaxy sees only "prepared" organics to be preserved, and their struggle with their synthetic children inevitable, and a dead end. That, too, is justifiable, and was only a minor theme in Mass Effect 1 (Shepard vs the Geth.) Unfortunately, the writing team simply didn't do it justice, as all can admit to. Especially using not one, but two Deus Ex Machinas.
Oh, and don't forget to Take Your Place in the STEEEVE!
Done by Generaal Lucas and Retrospective Introspective Videos, who were busy trying to put it together for me at the end of ME3:ECA8, I decided against it, as I am a heartless bastard. They, and a few others, are busy working on the Fixing ME3 series, which we're happily,
So, if anyone wants to try their best Arnold or Walken impersonation, to the immortal STEEEVE! scene, now's your chance. I'd happily draw some attention to your talents, and conduct an interview with you on all your geeky, video gamey, or other interests.