User blog comment:The Milkman/Mass Effect in Retrospect/@comment-4950455-20130417203249/@comment-2250460-20130419191806

If it's impossible, don't fault the game for it. I don't say "Yeah, well, you suck because you die. I mean, sure it's currently impossible not to die, but it's still bad!".

Shepard is still "defined", s/he has a goal of stopping the Reapers, has a close friendship with old squadmates, and it loyal to his/her crew. As to an arc, yeah, I'm pretty sure stopping the Reapers counts as one.