BioWare delivers a stellar finish to Mass Effect space opera

Mass Effect 3; Grade: *****; System: Xbox 360; PS3, PC; Published by: Electronic Arts; Genre: RPG; ESRB rating: M for mature.

Science fiction fans love their galactic empires. From the novels of Isaac Asimov and Frank Herbert to the multimedia epics created by George Lucas and Gene Roddenberry, the planet-hopping space opera has enthralled starry-eyed dreamers since well before the Apollo program.

With its Mass Effect series, BioWare has created the first video-game universe with the scope and ambition of Asimov's Empire or Roddenberry's Federation. But there's one problem: As Mass Effect 3 (Electronic Arts, for the Xbox 360, PlayStation 3, PC, $59.99) begins, the whole thing is about to be obliterated.

See, while humanity has been busy expanding across the Milky Way -- meeting a variety of intelligent species along the way -- an ancient race of machines, the Reapers, has been lurking. And now that we've gotten smart enough for interstellar travel, we're ready to be harvested. As Mass Effect 3 begins, the Reapers have invaded Earth, and the only way to stop them is by joining forces with all the other civilizations in the galaxy.

The task of uniting these diverse cultures falls to one Commander Shepard, the human who first stumbled across the Reapers in the original Mass Effect. If you played the previous games, you can continue with the Shepard you've already created; if not, you can create a new one. Shepard can be male or female, strong and slow, or delicate and agile, good with firearms, or adept with psychic powers.

Those aren't the only decisions you have to make. The species of the Mass Effect galaxy get along about as well as the various cultures of 21st-century Earth. The belligerent, lizardlike Krogan hate the high-strung, amphibian Salarians. The weak but clever Quarians are on the run from the mechanical Geth they created.

And there's one more wild card: a shady organization called Cerberus whose leader, the enigmatic "Illusive Man," believes the Reapers can be controlled rather than destroyed. Shepard cannot make everyone happy, and the choices you make -- some of which carry over from the two earlier Mass Effect games -- will affect your final battle against the Reapers.

It's much more complex -- and, ultimately, more rewarding -- than the binary, man-vs.-monster conflicts of less ambitious space-combat games such as Halo or Gears of War. During the 40-plus hours of Mass Effect 3, there's time for exploration, diplomacy, and even romance, and many of its most memorable moments involve simple conversations between Shepard and the crew of the spaceship Normandy.

Make no mistake: Most of the action involves combat against the Reapers and Cerberus forces. There's more to the battles, though, than just picking the right assault rifle and firing away. You and your squadmates also can use "biotic" powers to sling fireballs, combat drones, or miniature black holes at your enemies. And since this is a BioWare role-playing game, your powers become more intense as you accumulate experience. There's plenty of gunplay here, but it feels fresher than most of the increasingly generic shooters that have flooded the video-game market.

Mass Effect 3 lives up to every promise BioWare made when it launched the series in 2007. It delivers a tightly focused, urgent adventure while still letting you pursue your own path through it. It wraps up the stories of all the memorable characters you met in the previous games. And it makes you pay the consequences of decisions you might have made five years ago.

Now that I've reached the end, I want to replay the entire trilogy and see what I missed the first time. I cannot think of a higher compliment.