To the people defending the endings, I see your point. I really do. The endings themselves are not inherently bad. If developed well, they could have actually been quite good. But look at how it happened. The game was over, but then our ending was just snatched away from us. We go from an ending where the historic work that Shepard did, that we did, really mattered and paid off, to an ending where every previous choice we made was devalued.
The Reapers' goals and such, even the Catalyst AI, could have worked on their own, but they really, really should have been developed. As it was, they were pulled out with 10 minutes to go, when we're already past the game's climax (EDIT: The climax being the confrontation with The Illusive Man, btw)and not at the point where we want new elements introduced. Ever notice how, in ME1 and 2, you made your big choice BEFORE (or, in ME2's case, before round 2 of) the big boss fight? There's a reason for that: pacing. Momentum. Pulling out that sort of bombshell when the pacing was telling us that the game is over is just horrible storytelling. When talking to the Catalyst, Shepard looks and sounds dazed and confused, and at that moment, I felt the same way.
