Warning: Minor spoilers for Mass Effect 3: Citadel DLC to follow.
The very last piece of DLC in the last game of the Mass Effect trilogy is a few hours of unmitigated fan service, and if you realise that that's all it is meant to be, it is an absolute home run for Bioware. This swan song is jam-packed with references, in-jokes, and tidbits of lore, but if you know where to look, these asides are just window dressing on one of the best pieces of added content I've ever seen.
My three favourite moments in Citadel were an old ally's explosive introduction, Shepard and co stuck inside a vault, and the entire party sequence. What all of these have in common is that they are character moments. Bioware has, quite rightly, become famous for its character writing, and Mass Effect has one of the best ensemble casts in the medium, if not in any medium. It is a testament to this fact that a players preferred squadmates usually comes down to subjective preference, rather than a tangible difference in the quality of the characters.
Citadel is, above all else, a celebration of the people you've had by your side for however many dozens of hours you've explored this world. Every past squadmate can participate in a major way (barring two who simply can't appear for lore reasons, and happen to be two of my favourites -.-), and even a handful of the Normandy's crew get far more screentime per hour of gameplay than ever before. If you've played through all of the Mass Effect games, odds are you like at least a few of these characters, and it would be a disservice to yourself to miss out on this final farewell.
Now EA has taken a lot of flak for its business practices recently, no small amount of it from me, but EA didn't do this. Bioware did, and they did it right, so they deserve to be rewarded. This could have been one last attempt to wring more money from loyal customers, but the developers went above and beyond to make this one special. Well, the combat is a bit dull, but if this DLC is for you, you probably don't play Mass Effect for the combat. We play to experience the world and its inhabitants, and this is that goodness distilled to near perfection.
As an added bonus, if you're still upset about all the crucible nonsense, Citadel makes a much better alternate ending than the Extended Cut. Just play up to the signposted 'No Turning Back' mission, then do Citadel, then close the game with our heroes refreshed, their friendships bolstered, riding into the sunset on a high, if inconclusive, note.