I hope the internet shitstorm over the ending doesn't end up overshadowing all the great, great stuff that came before.
Somebody upthread noted Red Dead Redepmtion, which is probably the best ending to a game ever, but the thing that has stayed with me from that game isn't the ending. It's a small character moment they give to Bonnie: The last time she sees Marston in the game, as he pulls away on the carriage, you see Bonnie give the ground a little kick. It's such a small thing, but it's a nice gesture of her regret and resignation about things that she wished were different in her life.
Mass Effect 3 gives another moment like that. Not nearly as subtle, but no less powerful: When Shepard and Anderson are sitting down at the end looking out at the Citadel, finally grabbing a moment of rest, Hackett comes in over the intercom. There's just the tiniest pause before Shepard, injured but not quite dead, responds "What do you need me to do?"
That moment hit me right in the gut. Jennifer Hale delivered it straightforwardly, too, without a hint of anger. Shepard - my Shepard - was a goddamned hero, and if there's something left to do then she'll fucking do it, all right.
For me, that's the emotional pay-off of Mass Effect.