Note: This article has vague spoilers. It's not enough to tell you exactly what happened, but it is enough to spoil things for you. Use your head.
The fan backlash to the ending of Mass Effect 3 is unprecedented. The ending of Mass Effect 3 was the conclusion to an entire series, and it says a lot about BioWare that they could craft a universe that people care about this much. The outrage has built up to the point where important people at BioWare are promising to go back and change the game.
On one hand, I agree that the ending didn't work at all. It was shockingly bad and left me feeling frustrated and disgusted instead of satisfied and reflective. (My expanded all-spoilers writeup is on my blog.) On the other hand, I don't think a re-write will actually make fans happy. No matter how much we hate it, this is the story the writers decided to tell. If they change it to please us, then it's not their story anymore, it's ours. We can easily find ourselves in a situation where we're playing through our own fanfiction.
If you're looking for a good fanfiction ending then I highly recommend this one. It's dark and desperate, but it takes your actions into account and reveals the Reapers without turning them into a joke. But if you're looking for an official ending to Mass Effect 3, then you already have it. It even comes in three different colors.
In general, an audience is probably looking for three key things at the end of a story:
- Affirmation - Love conquers all, hope endures, freedom is worth fighting for, the truth will set you free, justice can't be denied, etc. You save the little kid, the evil overlord is defeated, somebody gets married, everyone celebrates the hero, cupcakes and ice cream. Ex: Frodo drops the ring into Mt. Doom and Saruon is defeated forever.
- Explanation - All questions answered. Making sure it all makes sense also falls under this category. Ex: How did Gandalf come back from the dead? What made the Witch King undefeatable? What happens to the Three Rings if the One is destroyed?
- Closure - How did things turn out? Did the characters have a happy ending? Ex: Sam married Rose. Frodo and Bilbo went to the Havens. Aragorn was crowned king.
Of course, there's quite a bit of overlap here, but you get the idea. Good guys win, questions answered, and character stories are fulfilled. Lord of the Rings does all three. The books are sometimes ridiculed a bit because of their drawn-out ending, but for me it's one of the reasons I love the series so much. The story is brought to a full and complete close and everything fits together.
Of course, you don't have to do all three. In fact, in a gritty sci fi universe like Mass Effect, a mega-happy ending can feel forced or out of place. It's perfectly valid to write a story where the good guys lose. (Empire Strikes Back, Se7en.) You can leave questions hanging. (What was in the unopened package in Cast Away? What was in the briefcase in Pulp Fiction / Ronin?) You can drop characters without resolving their stories. (What happened to Sean Bean in Silent Hill?) But if you are going to refuse the audience all three then you had better be really, really sure of yourself. You should have some kind of point you're trying to make. If your point is, "Life sucks, nothing makes sense, and you'll never know what happened" then you had better brace yourself for some push-back, because people know this already. They experience it every day in real life, and they probably aren't looking for more of the same in your entertainment product.