When I was a kid playing “Asteroids” on my Atari 2600 (still the best Christmas morning ever – thanks, Mom!), I remember inventing entire science fiction stories to go along with the onscreen action. In my mind, I was a daring space commander, navigating asteroid fields en route to saving civilization from some invading armada.

With the visually dazzling “Mass Effect 3” (PC, PS3, X360; rated M; $59.99), my childhood fantasies have come to virtual life. The final title in the trilogy, “Mass Effect 3” is state-of-the-art sci-fi RPG gaming. The blend of exciting combat and engaging story makes the “Mass Effect” franchise the science fiction equivalent of Bioware’s “Dragon Age” fantasy titles.

Those who have sampled the previous titles will already know what’s at stake: The malevolent race of sentient machines known as the Reapers has finally begun its invasion of Earth, and it’s up to you as Commander Shepherd to rally the troops from several different planets.

Combat is slightly tweaked from previous “Mass Effect” titles, but it’s still frenetic and intense. The third-person shooting style is perfect for the relentless cover-based firefights, and you can now slide around corners and otherwise maneuver while remaining screened from the bad guys. The enemy AI system has also been improved – opponents are smarter and more aggressive, and will often use team-based tactics to flank, frustrate and frag you.

If you’re more into story than combat, “Mass Effect 3” has you covered there, too. The game has three modes – Action, Story and RPG. In Story mode, combat is easier, conversations are extended and the narrative is much more interactive. In fact, if you’ve played the previous two titles, you can import your previous character and saved game files. Decisions that you made in the previous games will inform the storyline and endgame.

In the last few years, game developers in the RPG arena have been devoting more resources to storytelling – often recruiting science fiction writers and novelists – and it’s really paying off. The emotional stakes have been raised in “Mass Effect 3,” and there are moments that are genuinely chilling. The graphics and especially the sound design in “Mass Effect 3” are top shelf, but in the end it’s the story and characters that linger. Highly recommended.

Heavy Rotation: If you’re in the market for a lightweight side-scrolling platformer, check out the fun and funny “Fancy Pants Adventures” (iOS, PS3, X360). Originally developed as a Web-based Flash game, “Fancy Pants” has now been ported to PlayStation Network and Xbox Live Arcade, and just this month made the move to iOS, so you can play on your iPhone or iPad for just 99 cents.

As a platformer, Fancy Pants is pretty straightforward – you navigate a series of playfully sketched environments via a stick figure with some, yes, fancy pants. It’s particularly fun for kids, who will enjoy all the kinetic action and visual gags. Grownups and platformer veterans can admire the game’s elegant design and inventive use of in-game physics.

New This Week: Open-world action adventure in “Prototype 2” (PS3, X360), Celtic-themed historical combat in “Bloodforge” (X360), pirates versus titans in “Risen 2: Dark Waters” and 3-D platforming with “Shifting World” (3DS).