A little late to the party, but I just played the game with the MEHEM, aka the Mass Effect Happy Ending Mod.
It was very satisfying.
The Mass Effect series is by far the most profound and engaging experience I have ever had in gaming. There is exciting gameplay throughout the series, yes, but the writing, the characterization, produce some truly memorable moments. Moments of the kind that I have experienced once or twice in a small handful of other games, but which in the Mass Effect series occur by the bucketfull. I really can’t say enough about how much this series has meant to me as a gamer and a fan of science fiction.
Which made the terrible, horrible, literary suicide ending of the series really hurt. Although there was a bit of foreshadowing (the name, Shepard, for one, and Legion’s fate, for another) to the “Synthesis” ending, all of the endings, even those offered in the extended cut DLC, were, from a storytelling perspective, fucking retarded.
In comes MEHEM, the fan fix that redeems Bioware’s momemtary lapse of reason. Limited by the tools available, the mod only provides a small range of “happy ending” possibilities, but I always preferred a completionist Paragon Shepard, so this mod gives me the ending I was working towards anyway. It is perhaps a little weak from a storytelling perspective, but nevertheless it is a far stronger and more satisfying ending, one that fits the themes of the series, than the endings offered by Bioware.
And, in a rather meta sorta way, the idea that a single fan of the series, against all odds, refused to allow things to stand as they were, put in the effort and spirit to create a new ending, well, that’s just what we expect from a fan of the savior of the galaxy, isn’t it?
A final note to those interested in playing the mod: I discovred this page, which lists some new e-mails that the mod is supposed to add to the messages Shepard receives in-game. The very first e-mail doesn’t get loaded into the game, but IMHO reading it as if it had been included provides the necessary framing the story of the MEHEM needs in order to work, as a story.