After finishing the game I have to agree with almost all of those opinions about the ending. I liked the endings of ME (my fav one, including the credits) and ME2, and this one is just a bit off. Like some people have said, the whole thing about ME was about fighting against the odds and triumphing like a hero, narrowly surviving (note this part, I don't say owning the enemy or dying like a fool, but something in between).
Many of us expected that, after breaking his/her ass preparing everyone in all three games, Shepard would just defeat the reapers and enjoy a happy retirement (maybe in a beach drinking with Garrus

)... at least until the next galaxy-destroying baddie would appear haha. Instead we got those bittersweet endings that leave us thinking something like "... did I work that hard through the whole three games just for THIS?!". I'm sure Shepard would think that too, if he/she did exist and went through all that just for that ending

The game is great, and I really liked it for what it is (both the story and gameplay, even if I would change some minor things). The amount of losses that we face through the story made me a bit sad, in a good sense, and almost claimed revenge for it on my paragon Shep (well, I did it, in fact.... "this one is for Thane!"). For me, it means that I cared for those characters, and that's good writing and I love it. I was liking it that much that I was even thinking "wow, this one is the best of the trilogy".
However, like I'm saying, it goes down the toilet in the last 10 minutes (just after the "boy" appears and gives you the three choices, for more information). In my opinion, there's almost no difference between saving the galaxy from the reapers and letting them do their thing as, in the end, just a handful of people survive anyways. As explained, they reap every advanced civilization but leave the primitive ones alone. On the other hand, if you "save" the galaxy, all mass relays are destroyed, leaving everyone by themselves AND destroying every star system where there's one (do you remember what happened with some batarians?

). On top of that, Shepard dies. All that just for the chance for it to not happen again, as there's no guarantee... and even the "boy" points out that it will end bad. And that's the, in my opinion, "good ending". If at least good ol' Shep could barely escape and go with the Normady, I wouldn't mind this ending (and I think that most people wouldn't either). A new start with our beloved hero and his/her friends.
I won't say that I don't like the game, as I've enjoyed it, but I'm not happy with the bad taste that the ending has left me. It makes you almost forget about the rest of the trilogy.