Mass Effect, a sci-fi RPG by Bioware Corp., is basically awesome incarnate.
It melds the graphics and control scheme of Gears of War with the squad mechanics of Republic Commando, and puts in a team selection option similar to Blue Dragon. Level designs are reminiscent of Half-Life 2 and Halo3, but thats just the basics.
You have totally free reign over which world or system you ship, the Normandy, will go to. It's basically Oblivion in sci-fi, and the amount of details, backstory and quality that went into fleshing out the entire universe is awesome. Every race has a backstory, even extinct ones. Wars are catalogued, attitudes of alien species' vary greatly according to their history with another race. Even your crew members have varying attitudes.
This game basically immerses you so deep into the universe that you'd feel for your crew and team, and it really hits you hard when you're forced to make hard decisions, like living one of your crew behind in order to save another, or deciding whether to condemn an entire species to extinction or continue with your mission.
Complimenting this is an excellent dialogue system that is fluid to an extent whereby IF the player wasn't concentrating on which dialogue options to shoose from, it'd fit right into the silver screen of a sci-fi blockbuster.
Gameplay mechanics aside, the graphics are awesome, and the music sets the mood perfectly. Expecially after a mission where you lose a crew to the main antagonist. Walking around you ship feels just like an episode of Battlestar Galactica (reimagined), which means its awesome for sci-fi fans.
Except for the slow texture loading speeds (which I believe can be attributed to frame rate needs) and disappearing bodies, this game is GoTY content. If you have an XBOX 360, get it immediately. If you haven't got an XBOX 360, get one, then get it. It's an experience you'll never forget soon enough.
I'd give it a 9.8/10 anytime.