I read Avatar's post before going to the game store and was curious what the clerks thought of the ending since I haven't played any of the games. I'm not saying they are the "be all, end all" of opinions but I generally give them a lot more credit than most clerks (like those at Gamestop who make me want to smash my head against things sometimes) and they seemed to be on the side that wasn't too impressed.
Still, and correct me if I'm wrong, but wasn't there something about Mass Effect 3's ending that was leaked during development? That may be an urban legend but if that part of the game was compromised that may explain why it seems so stilted.
However, Avatar does bring up a good topic. I'm usually more disappointed with mid-game twists than I ever am with endings. A bad twist can make or break a game but by the time I get to the ending everything is already said and done. That said, here are a few oddball endings that stick out to me:
SaGa Frontier (Blue's Scenario): This is an odd one because it's a matter of opinion what the "ending" consists of. If you consider everything after striking the last blow to the final boss as the ending, all you get is the screen turning black and white upon that exact moment with the words "The End" on the screen. However, a lot of people consider the one-on-one duel before this point the as the "end" since the credits roll afterwards, making the fight above more of an "interactive" ending. It's totally up for grabs how you interpret this but it's more-or-less the result of running out of development time.
Mega Man Legends 2: Not so much odd as in desperate need for a sequel... but we all know how that turned out. I don't know how you could watch this ending and not want more story.
Mega Man X8: Do NOT even get me started...