I'm sure nothing I'm going to say here is new, but I figured I might as well chime in as long as you guys are doing us the courtesy of listening. Let me say, first and foremost, that ME3 was impeccable (save for that ending bit). I don't think any entertainment has ever pulled at my heart the way this game did, and it is truly a testament to the brilliance of the team that so many share this exact sentiment.
I don't even know where to start when it comes to the things I liked. The interactions with the crew felt natural, and were just the sort of conversations you would expect to hear from "old soldiers." These people have been through hell together, and the worst is yet to come. That notion hangs heavy in every word they say, and the voice actors deserve heaps of congratulations and recognition for their performances. Seriously. This game gave most movies a run for their money in terms of drama.
In addition, I felt the action was polished and tight. The old problems with sticking like velcro to any surface with a three meter radius was pretty annoying, but I won't hold that against the rest of this game. Using abilities and powers felt natural, and was implemented well. No qualms there.
The story was also commendable... all up until the end. What would I have done differently? And here's where I have trouble putting into words what EXACTLY I would have done differently. The big things that really haunt me in the wake of completing the game are as follows:
The Catalyst — As soon as the Starchild came waltzing in from stage left, I started with the questions. Who is this? Why does he look like an incorporeal version of that kid that Harbinger killed in the opening scene? Speaking of, why isn't Harbinger here confronting me? Isn't he the main villain in all this? Why is the Ghost of Reapers Past lecturing me on the created rebelling against the creators? Does that mean that the Reapers are going to rebel against him? After millenia of haunting the Citadel, did this not occur to him? I hate having a new character with as much would-be importance as the Starchild introduced in the final moments of the last act, especially with so little clarity as to his origin, his purpose, and why, oh why, does he look like a boy from Earth?
Decisions — The three decisions were rushed and, while in theory very different, very similar in their explained end-states. Swallow the blue pill, and you can fly the Reapers away and let civilization continue. Except... where am I flying the Reapers away to? Are they coming back? Am I now a Reaper? Yes, the day is saved, but at what cost? This is an area where a little scope after the ending would show what implications this decision has on the Galaxy in the future.
Okay, but what if I choose the red pill... all the Reapers die, of course, and so do the synthetic life forms in the Galaxy. Except, how does the Crucible decide what is and is not a synthetic life form? The Starchild says that because I have synthetic implants, I, too, will die. Does that mean everyone with a prosthetic leg or a pacemaker will die, too? Again, the ramifications are introduced as being very limited in scope (as limited in scope as genocide can seem, anyway), but the Starchild's idea of synthetic life seems a little too inclusive if it means that Shepard must die along with the Geth, Edi, and the Reapers. How do you fix this? Simple: Swallow the red pill, and the Crucible acts as a giant space antenna to shut down the Reapers. Their life switches off, they crash and burn, massive shells left orbiting the civilized worlds of the Galaxy. Anything dependent on the Reaper code would also switch off. If that means Shepards implants are based on Reaper technology, at least we now have a reason why he must die. It elminiated "space magic" and gives us a logical reason why choosing the would-be "Renegade" path results in Galactic extinction of synthetic life.
But lest we forget the green pill. The only question going through my mind in this portion of the ending was "How in the seven hells does that even work?" I don't know how to salvage the green option. For a series that has operated within the bounds of Relatively Acceptable Sci-Fi Mechanics, introducing this level of "Poof! You're Robots!" space magic is painful. I would scrap this ending.
War Assets — The whole Galaxy is on fire, and I'm running around digging up Kakliosaur bones from some moon to give to some guy I overheard on the Citadel. Cool. How does that influence whether or not Starchild and the Technicolor Space Explosion incinerates Big Ben and the people of Earth in the final minutes? I'd rather see them employed in some nerd-fest, brainless sci-fi action. I've spent 100+ hours through all three games kicking butt, now I'd like to sit back and watch the combined fleets do their stuff. Hordes of Krogan rampaging over armies of Reaper minions, while towering Geth Primes lay waste to enemy forces. I want to see the highest of pew-pew laser violence as the orbiting Reapers fight off the organic resistance.
And if I didn't unlock a brigade of Asari Commandos, I want that to impact the battle. I want Paris to burn to the ground because I screwed up the relationship I had with the Krogans. If I let the Geth wipe out the Quarians, or vice versa, I want there to be a hole in the fleet that tips the favor to the Reapers. If I let the Destiny Ascension get blown up in the the first game, I want the Asari to get pummeled by the Reapers to the point that they have to limp away from the fight.
Break up the War Assets by species. If you don't have a high enough score for each species, have that impact their galactic standing afterwards. Have that impact the battle for Earth! We want to see that happen on our screen. We don't want to speculate on it aftewards.
Denouement — There are so many other problems with the end, and I don't even know how to approach them. Explalin why Joker is running away. How did the crewmates who were running with me to the beam decide to turn tail and run back to Joker while Commander Shepard plays John Wayne with Marauder Shields.
This part of the story—the ending— should be focused entirely on denouement. Wrap the story up. Don't introduce new characters, don't gloss over the ramifications of our decisions, and don't offer us skimpy and unsatisfying glimpses of our crew on a jungle paradise without telling us WHY they left their Commander to die, and just how they got there. And then what happens?
A number of reviewers have argued that this whole game is denouement, and I agree. But don't spend ten or more hours on wrapping up the plots of the entire series, only to unravel them all before saying THE END. Which leads me to...
Catharsis — By undoing all that wrapping-up, everything we had accepted in the game so far comes into question. A lot of good people died under my tenure as Commander Shepard, and I accepted their fates as a necessary step to vanquishing Evil from our Blue Marble in the System Sol. But if you're telling me that all their sacrifice resulted in was the destruction of interstellar travel, the abandoning of the combined might of the galactic fleets, and, potentially, everybody's suddenly robots, our investment in the story gets nullified. We spent the whole game accepting and coming to terms with the ramifications of our decisions, only to have them whisked away and replaced with inferior options.
Yes, I get to make a choice, and yes, I get to watch any one of three endings with the varied color palette of a box of crayons, but my emotional investment in the story is left... wanting. In completing Mass Effect 3, I don't feel completion, or satisfaction, or catharsis. I just feel like I wasted my time.
I won't pretend to be a game designer and tell you how to do your jobs. I just want to let you know what was going through my mind in the final moments of this near-masterpiece you've created. I've been a fan of BioWare's talent of creating immersive, deep, and textured entertainment since Baldur's Gate, and I want to continue to be a fan for as far into the future as I can see. I hope these points are helpful to you, and I hope you are sincere in saying you will listen to your fans. I have every confidence that you'll make release something that will provide a sense of closure to this gem of a universe you've created, and I look forward to the coming days to see what you come up with.