Some spoilers below, but nothing which should be too major given this thread:
I think Bioware has definatly shown they have lost their touch. Going from quality RPGs to shooters and brawlers with cinematics, and now increasingly bad writing in some of their strongest franchises. I had my problems with the story in DA2, but this seems to be even worse on so many levels that I'm kind of shocked that the same people who did the first two games wrote it.
THAT said, I think what your looking at is EA's influance here. See, Bioware itself tended to be smart enough to know when a story was over and wrap things up properly and leave them. A good example would be Jade Empire, a game that was pretty well self contained, and proabably would have suffered if they attempted to turn it into a trilogy or full franchise. As a result they seemed to pretty much leave it to stand on it's own, figuring it would only be re-visited if some serious lightning struck.
When Mas Effect was originally planned there seemed to be an intention that they were going to do THAT story and not worry about turning it into a huge franchise. As the series succeeded though you'll notice things very rapidly switched to comments about how the triology would not end the universe and how they planned to spin this into a huge franchise. While superficially good news to fans, it does tend to weaken an overall production as actual finality and wrapping things up might be sad, but it's usually for the best rather than dragging something on until it bcomes a mere shadow of itself and dies.
The endings we're looking at all seem like franchise starters, and probably weren't intended when the series was first conceived, hence an outcome that doesn't match the tone of the game.
From the perspective of wanting a franchise what these endings do are perfect. They remove the player created character from the universe as either being dead or vanished (ie a subtle implication of possible survival in some form from what I was reading), likewise it's possible that any of the Bioware created characters have lived, and as faces for the series could thus be used in other products. The amount of damage having been done to the universe allows an excuse to pretty much re-write lore by saying this or that was lost, or one species didn't survive, or another came to unusual prominance, or whatever, without being tied to the balance carefully constructed to the codex. Basically they could toss out a lot of the trappings of Mass Effect (aliens, etc...) without have to worry about pesky canon since they gave themselves an excuse to ignore it and slap the Mass Effect name on something vaguely similar if need be while claiming connection.
It's a classic gimimick with salable fantasy worlds, it's obnoxious, but apocolypses are good for business, the guys doing D&D learned long ago that they can make bank by periodically wiping out The Forgotten Realms in order to change things around, and re-sell sourcebooks on the same regions without having to do a lot of work, or worry about have changes in game mechanics between editions might cause problems with how history turned out (ie due to the removal of, or changes to spells or the casting requirements thereof that were used to justify the feats of certain cities, or how things played out at specific times).
Basically you could call this the Ma$$ Effect ending, the story being wrapped up in the way that was the best for marketing.
Incidently EA and Bioware (and really I'm going to point fingers at EA calling the shots no matter what Bioware says, because things HAVE changed since they took over), have probably learbned from comic books, RPGs, and other things, that fanboys are stupid. An ending that pisses people off can be an absolute marketing goldmine, because rather than just turning their back on a franchise after saying "that sucks", fanboys will whine but buy all the products hoping they will eventually "fix" things or recapture the old magic. Periodically throw out a bone or a hint that effect, and you can sell even the lamest products and tie
in events.
Look at it this way, for all of the fan rage does anyone for a second believe that a substantial number of pre-orders were cancelled by these reveals. Heck, I'd even suspect the leak was done on purpose (which is why Bioware confirmed the original script and so on) because raging fanboys will tend to buy a product just to see if it's as bad as they were hearing so they will have something to QQ about.
Just watch, come the 6th, Mass Effect 3 won't exactly be a failure. What's more this last minute "spoiler" has generated hype, and plenty of people who otherwise might not be following it are now having their attention drawn.
So really, EA/Bioware is probably just sitting there hissing "Yeeesss, give me your hate" with Papaltine-like glee, as continue to leech your money in an ever expanding flow as a result. While eagerly anticipating the cash-sucking franchise they have just created an ideal set up for (blank slate of a world due to a canon apocolypse, with a well loved name attached).
If you want to make a differance, don't buy Mass Effect 3, make sure nobody you know buys it. Enough people do this, and EA/Bioware will actually get theirs for once. However the odds of anyone really cancelling the game over this, never mind enough people to matter.. pretty much non-existant. We fanboys are nothing if not predictable, which is exactly why we see people exploiting us this way. We're like farm animals being harvested, we might not like it, but we are incapable of altering the behaviors that put us in that position... or to be more fear we refuse to alter those behaviors, in part because of our own herd. We remember Mass Effect being a big social thing in our community, that everyone could talk about, and don't want to miss out on being there for that again, even if the community all hates on it now, it's being part of something.
Ah well, I'm rambling, but that's my diverse thoughts on the subject.