Coming in not from a Mass Effect fan standpoint, but instead from a massive Fallout fan POV, I really have to say, the multitude of people bringing up Broken Steel really don't seem to get how far off the two situations really are. Massive spoilers inbound, but there's really no other way to discuss the two reasonably.
Let's sum up; Bethesda created a massive open sandbox game with a central theme; sacrifice. It's a running theme through the whole of the central storyline. What are you willing to give up to achieve an end, to save lives, or to change the world? The Lone Wanderer's mother died giving birth to him/her. The father sacrificed himself to protect his life's work. If confronted rationally with how dangerous and destructive their plans are, both President Eden and The Overseer surrender their dreams wholesale, their negative effects in the latter case negated by rational choice and in the former upheld by a man who seeks his own ends. Even in the simulation, the 'correct' path from the game's karma standpoint is to kill and free the eternal prisoners, leaving the instigator alone eternally. And in the end, upholding this theme, the Lone Wanderer is expected to sacrifice himself, or conversely allow Lyons to sacrifice herself, to save the Capitol Wasteland.
The problem being, whether you looked at the story and enjoyed it, or hated it, following through on the theme had the unfortunate side effect of ending the actual GAME part of the game. Once you make your sacrifice... well, that's that. Game over. You're radioactive worm food. Cue Ron's narration and a few still shots relating to your actions. From the perspective of someone who enjoyed the story arc, I understood it. From the perspective of a player, I was pissed. It felt like it betrayed the very idea of having this massive world to explore that I didn't get to, well, keep exploring it.
Bethesda themselves realized they'd kind of shot themselves in the foot, and responded in a way that prevented the arc from being undone; the sacrifice is made, but the player survives. But rather than just fix it, they added new missions, new subquests, new weapons and enemies, new locations... simply put, they made a full and worthy expansion. Fans were happy to pay up, because it wasn't just a fix, it was an expanded game experience, and paved the way for future expansions and a widening of the storyline. To this day, I can still go back to Fallout 3 and have a good time, partly because they fixed what I felt was the one big glaring flaw... well, that and not getting to aim for the eyes or the junk like in the first two games, but I digress.
However, with Mass Effect 3... you have a very different problem. Let's put aside the artistic arguement for a moment here and consider the ending(s) on display. Yes, they violate the arc up to that point. Yes, they defy the lore. And yes, they're not very... well, satisfying. And yes, they're in direct defiance of what the game was sold on, the idea all your choices would matter in the end and would impact the endings, of which it was claimed there were far more endings then the game reall shipped with. On the surface, it's F3/Broken Steel all over again.
The issue, however, is that it's not. The Fallout 3 problem was with the GAMEPLAY. I can't emphasize that enough. Fallout 3 ended the game when you put in the code and fell over, credits roll, done. Fans pissed, Bethesda's not overly satisfied either, so out comes Broken Steel to change that while also adding a lot more to the game itself.
Mass Effect 3, however, finds its problem in the story, and that way lies madness. The game itself, as shipped, has a damn bad ending by most accounts... most being the key word here. Some folks liked the ending. Some didn't care and were more interested in the road to get there. Some folks couldn't give a toss about the story and are in it for the gameplay. As with F3, the dislike isn't universal. But with F3, the fix more or less made everyone happy; if you liked the original ending, then you didn't have to get Broken Steel. Your Wanderer falls over dead, game over. Hell, even buying it didn't revoke the fact that you STILL had to make a choice, STILL had to have someone put in the code, and even still got the effective ending cinematics et al.
ME3, on the other hand... well, look at all the camps we have. The ones who want the option to just fight it out, damn what the Deus Ex Machina offers as choices. The ones who want the option to point out their own Perfect Paragon-y actions as proof it's full of shit and the three choices are all flawed and based on faulty assumptions. The ones who want it all to be indoctrination. The ones who want to keep their existing endings, either because they liked them or because they feel the artistic integrity is compromised otherwise. The ones who don't care about that part, but demand an epilogue that explains what happens next. And, undoubtedly, a fair few more I've skipped.
What all of these ultimately have in common is that they are purely story-based. Few are asking to fight the Catalyst as some special boss, or use some alternative method that involves dog-fighting the Reapers down to save the day like Master Chief with variable gender and sexuality. They want the STORY to be fixed, because THAT is where it fell apart for them.
The question then ultimately becomes very murky, even from a purely mercantile capitalistic perspective; if Bioware/EA released the new ending(s) for free, then that's a lot of cash and resources out of pocket that aren't likely to come back. If they make it actual paid DLC... then they're utterly boned, because players could easily just watch it on YouTube instead and ultimately miss out on nothing. There is no gameplay, no additional game part of the game, to be harvested here. And without that, the legitimate incentives start to peel away.
Furthermore, story is a tricky beast. Especially story set in such a way that the player, ultimately, shapes the story within a very extensive framework. The survival or death of countless characters, even whole species, is in play. Yes, it was a cop-out to not ship with the endings promised, even verging on false advertising. But asking for a do-over now really is setting yourself up for disappointment on all fronts.
Where would the do-over begin, if one were not to simply tack on an epilogue? Would you change everything in the final ten minutes? If you did, you'd piss off the people who wanted the ending(s) to remain. Would you add new unique options for the player to select, new routes to take dependant on certain actions throughout the trillogy? Well, what if someone didn't take those new routes? How many routes are on offer here? How many choices, and which ones, should add up to those new choices? Should it be purely dependant on Paragon or Renegade? If so, wouldn't that in and of itself still not be fufilling, given it ignores the REASON for the label in favor of label-alone? And again, ultimately, if there is no additional gameplay, how many people are actually going to pay to see it as opposed to just watching videos of it online?
Again, this is just one poorly-informed soul's view on the matter. Take it, leave it, whatever you will. I just wanted to poke my head in and clarify, in my opinion, how comparing this situation to Broken Steel is a faulty comparison at best.
