the way it is now, the victory is completely phyrric. yes, you beat the reapers.. or something, but at the cost of the established lore. I mean, the end of the mass relays means the end of galactic society, it probably means the death of the Krogan (trapped on tuchanka with nothing but dirt), the death of all the turians on earth (they're dextro DNA remember?) and the stranding of hundreds of thousands of members of all the different species everywhere. I mean, I guess you won since they're all alive, but it feels incredibly hollow. Not only that, but the endings are all functionally identical. they're all black except one or two of them are in a slightly darker black.
I've heard the argument that since the entirety of ME3 is the ending of the series, and since the choices in ME2 do change the course of ME3 it makes for a unique experience. I guess I can't argue with that, but the fact that the END of the end is the same pretty much across the board makes that feel like a cop-out. Theres a lot to like about ME3, but the ending is just so incredibly lame and horrible that it destroys all the positive feelings about the experience.