It wasn't written by a buffoon
Star Wars purists can say what they like, there's no denying that Mass Effect is a better-written piece of fiction. Too long has Mr. Lucas pondered over tiny details, tinkering with his own creation until it'll eventually collapse under the sheer amount of tippex coated around the edges.
Worse than the thousands of re-cut editions Lucas may one day unleash on the world are his one-dimensional characters. Exceptions to the rule arise here and there, but for the most part the script is dire. That isn't discredit to the actors, of which most are class-A, but to the shoddy script they had to read from.
Episode 2's romance scenes are beyond comprehension, bogging you down with awful one-liners until you're left writhing on the floor, contemplating popping your eyes out with spoons and then stamping on them.
Mass Effect on the other hand is a team effort, and it shows. It's by no means perfect but we can confidently say there isn't anyone involved in its creation actively striving to turn it tain it. We can't say the same for Star Wars.
What's more, every line of dialogue is thoughtfully written, it carries weight and has real impact. Narrative is the driving force in Mass Effect, romance, loss and all those other things Star Wars fumbles its way around are explored with with conviction an assuredness in Mass Effect.
The only exception is Shepard's dance moves, which are a galaxy-wide disgrace.