ME has no peers, which is both a merit for ME, and shows something unfortunate about the game industry in general.
As for contribution to SF, it's contributed largely in a resurrection of science-fiction as an actual gaming environment. Not science fantasy. Not "science fiction" where there's no actual science, just "scientific-style" stuff, and not just as a vague, unimportant background, but actual SF which has a couple of hyperscience principles, and then goes with real science from there. That's something we've not seen much in games, movies, or TV for a long while. Stargate was the one show keeping that alive on TV.
As for "new and original", it's really just reconstructed various SF tropes, and deconstructed others. ME doesn't seek to be stunningly new - indeed, you'd be doomed trying to do that and make a good game at the same time (a book maybe), I would suggest. Most people would spend most of the game trying to figure out what was going on. Instead ME takes all sorts of standard SF stuff and look at it again. In many ways, it takes what Babylon 5 was doing - creating an SF universe and then making it more realistic - right down to the political squabbling and greed and so on, and then goes a whole lot further with it. The whole situation with the Krogan is an engaging moral dilemma worthy of virtually any SF writer, and far beyond the sort of thing we normally see in TV and movies, for example. It's complex and not black & white, and that's something that ME has focused on. That's something I hope it never loses, too.
As noted, there are no "peers" to separate itself from. No comparable SF CRPGs exist. No fantasy CRPG is particularly similar.
Story-telling-wise, the main breakthrough is in quality and intensity, rather than anything "original". I don't think ME has done anything that hasn't been done before - it's just done it far better. I hope it continues to achieve this standard of storytelling.
Finally I think ME's visual design, sound design, and music are so far ahead of other SF-ish game franchises and even TV franchises that it's absolutely amazing. ME has a much stronger and more consistent "look" than either Star Trek or Stargate (let alone B5 or the like), with only Star Wars being arguably ahead (through sheer volume), This is a true achievement. Out of nowhere, BioWare have pulled a fully-formed SF franchise, which looks so distinctive and so strong. The music is also certainly ahead of Stargate, and I would argue, comparable with any major SF franchise.
Comparing to other "SF" games like Borderlands or the Gears of War series or even the Halo series, they all look absolutely terrible by comparison. All of them have narrow looks, utterly reliant on cliches and frequently on, sad, overworn, ripped-off of visual design. Halo's visual design was seemingly impressive, but compared to ME, it's really not at all impressive, and seems far more cliche-ridden and less "classic" than ME's design.