Mass Effect 3's Consequences Problem
It's not the ending. Not exactly. I don't really care about the ending, or whether it made sense, or whether Shepherd became a god, or whatever.
Mass Effect 1 gave you a game-long conflict with the Council and then built a believable context in which the choice that determined the fate of the Council would end up in your hands. Your investment in this late game decision was built up over dozens of smaller decisions over the course of the game. Whatever choice you made, it would be a reflection of the character you'd played--how they respond to antagonism, what they value.
Mass Effect 2 did that even better with the suicide mission. That entire game is a series of personal stories centered on learning all about the team who will live or die at your side, based on your understanding of their strengths and weaknesses and the time you've spent earning their trust and winning their loyalty. The big choices that determine the outcome of the suicide mission are all reflections of that journey.
For me, everything about the choices of Mass Effect 3 (save, perhaps the genophage) was too big to be personal. It felt wrong to be the one making this decision. It felt like the fate of the galaxy should hinge on more than just whether I pressed this button or that button.
I can't remember much of what happened in Mass Effect 3. I don't have a catalog of individually memorable moments. It felt like a stream of "this is the finale" disconnected cameos, determined at any cost to neatly tie off all the plot threads introduced in earlier games.
And maybe, after all, that was the problem. Maybe Mass Effect 3 was too set on being an ending. In ME1, when you make your decision about the Council, it's with the knowledge that life will go on--Shepherd and everyone else will have to live with the consequences of this decision. In ME2 also--each comrade who lives and dies by your choices is a person, a life that will continue or be cut short. In ME3 the consequences of your final choice are too massive to imagine and too complicated to explore in the brief denouement that's given. Everything about them is too abstract, too bloodless, and with all of my friends' personal stories resolved, I didn't have anything left to care about.