It has 2.1 or 2.2 stars on amazon. I don't think I've ever seen the public be this hard.
For instance some of the other most hated on games this gen FF14 has a 2.4 stars or Dragon age 2 with 3.3 stars.
Now I personally think FF14 is actually that bad, and Dragon age 2, I've never been sure how I feel about it (it's dumb downed yes, but I like the characters, and the gameplays still really fun), the dungeon re-use was quite inexcusable since they are in fact different dungeons, that are the same dungeon.
ME3 people I think aren't being so rational, and people are being big babies about it. Even if they are dissapointed (I am a bit). It's a videogame, things are not going to be exactly how you want them. Your desicions do affect the game, but don't affect the ending. I thought a lot of the things were taking the easy way instead of making your decisions more meaningful, but that's kinda the way Mass effects been the whole series. In ME2, killing the council has really no effect on the game.