I honestly don't think the endings are that bad.
It's kind of weird how short it is.
What EA should have done is give us a ID4 ending. I think most of fans would be much happier with that kind of happy ending. Maybe even throw in a parade to give a homage to Star Wars.
I can go on and on to explain why EA, being a greedy bastard, has no right not to give us a cheese happy ending.
However, I am not visually upset up these endings. I think the reason is that I, as an avid sci-fi reader, has never considered the main plot/premise of Mass Effect 1 "good sci-fi", therefore I have never emotionally invested that much in the premise. I actually am not sure if I understand why some gamers are so upset by these endings.
I want to compare the endings to Akira or Evangelion endings. But if I do that I would be giving the ME writers too much credit. My main problem is that they don't feel closure.
I think somebody can edit a good ending out of the materials that we have:
Keep the EA plot up to inside the Reaper thing, we see Sherperd meets Anderson, and they said "we did it.." and then emotional music start playing, we have images of the Citedal opening up, sending out shocking waves to destroy all the reapers; and then music keep playing, you never get a visual confirmation what happens to Shepard; and we start seeing rebuilding scenes, these rebuilding scenes need to be long, and the music need to be good; hopefully we see all the major characters in their home planet starting a new life after the war; and the music keep playing; and cue BioWare logo.
I would be very happy with an ending like this.
To me personally, there are some very powerful scenes in ME3 (in the middle of the game) that I consider some of the best in video game. I might still pick it as my GOTY.