I thought I would add this as more anecdotal evidence. I had 3.5 hours to play from the point you go to earth. I planned 2 hours to finish the finale and than some extra time to play multiplayer.
After I finished, I had to replay the ending to see another choice. Than I went to the forums to finally see what people were saying.
I loaded the game back up and stared at the main menu for several minutes and I couldn't bring myself to load the multiplayer.
Dejected I load up TF2 (hat simulator) instead and hop my server with our regulars that I have been playing on for years. First thing they say is "hey haven't seen you in awhile".
I replied back with ME3 was so good I couldn't put it down, but I just finished it and wow... I really don't know how I feel about the ending.
I didn't want to spoil it for those so I said I felt like someone stole MY ending and gave me a ending to something else. For the first time I wasn't engaged in the story. My choices didn't matter. I felt like I was robbed of something valuable.
Everyone let it go but shortly after I was doing horrible and just couldn't seem to do well at all. I normally frustrate people by deflecting objects with they pyro, but that night I couldn't do it. They commented on it and said it appeared I was having an off night.
I said the ending shook me up that much.
One person told me was getting a gift card to amazon and he was planning on getting the 3rd one but after that he said he was going to hold on. It wasn't my intent to stop people from playing the game solely based on the ending but it happened.
Since then, the regulars I have talked to, have asked me about it, and I without trying to be a boycott person, people evaluated their purchase.
No one wants to finish a game and feel as if it was pointless. My choices didn't matter and it bothered me so badly that it wasn't addressed.
People said they didn't care if Shepard has to die, or if Earth didn't make it, or the reapers didn't die. But when you tell a person their choices don't matter, especially in a Mass Effect game, that has some real stopping power, because the choices all the way to the end meant something more than most games.
Even the most depressing Epics can leave you with very powerful and upsetting emotions, but you shouldn't feel like the victim, like you were robbed of what was supposed to happen.