Therein lies what seems to be the main difference between the people who enjoy the ending and the people who don't. Fans who enjoyed the ending seem to have experienced sacrifice and loss constantly. Losses on Virmire were the first, but the Suicide mission's losses compound that, and then the deaths in ME3 work neatly into the 'loss, sacrifice and death' mood that has been built up in their game style. 'Scripted' deaths in ME3 can be a part of that, and if you didn't play ME2 well, then they're compounded constantly.
The game is geared for someone who didn't save a lot of people. The endings are all geared towards that. IT's all fine and good, but what about the players who haven't lost people every step of the way? That's the issue, the game is only satisfying and fulfilling for players who have lost. The players who saved their squadmates, worked through problems without making an arbitrary 'this or that' choice, the players who saved Wrex, who made it through the suicide mission without a loss, who only lost characters when it was completely unavoidable (and even then, they died because of their willingness to give everything for a better cause, a noble death in cause of something worthwhile).
It's a tone shift for players who don't 'lose', there's no ending for us. There's no resolution for us. For those of us, we've come to see the game as being one where we can overcome the worst and most maddening conflicts, where we overcame things that people said no-one could overcome, solved problems no-one could solve. That is the problem, there's three endings to chose from, but in essence, it's the Hobson's Choice, you get the same result, no matter what.
You're either dead or in ruins, your crew is lost, the galaxy is decimated, the mass effect relays are gone. At the end, the people you care about, the central aspect of everything that the game has been about, Character Development, Character relationships, is discarded and the central reason for investment is gone, your crew is marooned somewhere (Zorya actually) that you can't reach.
No matter what, the tone of your character and the relationship you have to the characters you've been invested in is the same.