Bioware told us that they care about their fans, customers. I don't want to complain about why the endings are bad, or good. You can find plenty of explanations out there on the internet.
So I just want to share my thoughts about what I would consider a good ending for Mass Effect 3. (I am not a native speaker. If my english is weird sometimes, sorry

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Well, allow me to write it down. Just ideas. The game what Bioware created is awesome! Every single game what they created in the last decade is amazing! Ah you know what I just spit it out: MASS EFFECT 3 is their f*cking MASTERPIECE! If they decide not to change the ending, than it remains the same MASTERPIECE in my eyes.
But they asked our opinion regarding the ending so here is mine:
I think Mass Effect 3 need some vastly different and distinct endings.
So, I think at the END of the trilogy the game doesn't need that space kid. It's just destroys the lore of the Reapers exsistence entirely. So cut out everything after Anderson dies.
Oh yes, and that means Shepard doesn't have to choose anything at the end. That's the point!!!
Why? Because, our earlier choices will determine the actually ending of our saga. And that's it. No space kid, no last decisions. Just what Shep did in the last couple of hours. And YES If you want to see the other endings of Mass Effect 3 you have to play the game again, with a different Shepard. Not just quick load, and let's see the other one.. No. no.nonono... That would be too easy. You already made your choices, just like in the end of Mass Effect 2, here comes what happens next:
1, VERY BAD ending: What you guys at Bioware created. Minor tweaks of course would be necessary, but that shouldn't be a problem. First of all, cut out the Joker sequence. No need for that. Shepard dies alongside Anderson. The Citadel will blow up, the Reapers will die, Earth will be incinerated. And because every single Mass Relay in the galaxy is going to be destroyed, that means one thing. Every solar system, every species in the known universe is going to be completely destroyed. That's it. THE VERY BEST BAD ENDING.
2, BAD ending: Same scene. Shepard dies alongside Anderson. But the Citadel and every Mass relay will be intact. Of course the Reaper army will destroy the entire galactical armada, and they will finish what they started. The cyle of our destruction will continue. New scene: 50.000 years later: A new alien species discovers the memory box what Liara created. And when the Shepard VI tries to warn them about the Reapers, in that moment, they hear that terrible sound. They look up to the sky, but it's too late, the Reapers are already returned! (Admit it, it's a bad ending, but it's god damn epic!)
3, GOOD Ending: This is the hardest part. Because this is when you have to show what we did in the game mattered. In this ending Shepard will survive the war or not. And to survive the war, he/she needs two criteria. 1, High enough Paragon or Renegade score, and high enough EMS score. If the Paragon and Renegade scores are not high enough, he/she dies, but the good ending still plays if the EMS score is high enough. So here are the variations:
3/A: Shepard is dead. Now you have to show what he/she has accomplished. The major decisions are the most important.
1, Krogan-Turian conflict: cured Genophage, or not (peace or war)
2, Quarian - Geth conflict: peace, Geth survived, Quarian survived
3, Rebuilt Citadel, rebuilt Thessia
4, the crew! some minor things about what happened with them, Liara wrote a book about the protheans, Tali built a new home on Rannoch, James earned the N7 title, etc.... (the guys at Bioware know this better than me. I trust them, I always will!)
3/B: Shepard is alive. The first 4 are the same. And we have a 5th one!
5, Shep and his/her Love interest! Yes this is probably the hardest part. Because there are so many of them. That makes the story more exicting and adds replayability to it!
So there it is! My ideas, and opinion about what I consider a great, satisfying, most of all worthy ending of Mass effect 3.
Secret ending for New Game Plus: If Shep is alive: High enough paragon, or high enough Renegade score will determine his/her life after the war.
1, high enough Renegade score: He/She is a new Admiral in the Alliance fleet!
(Imagine the fans reaction... Yeah that's what I am talking about!)
2, high enough Paragon score: He/she is the new human represantative in the Citadel council!
(again... imagine the fans reaction! .... Yeah that's what I am talking about!)
Pure epicness, pure awesomeness!
I just wrote this down because Bioware doesn't deserve our hatred. They need our support, and new ideas! They worked hard to create an awesome experience. And I think they just did that.