certainly if you don't write about saving the world, the next guy will. and if his story is better than your's, he'll sell his before you do. i think it's about that simple. if you don't like save-the-world stories, just don't write them, but if you want to get into that no one here is going to talk you out of it, lol.
as far as being cliche, just about what isn't? i can hear someone out there say, 'but, preyer, my man in a special suit is different!' yeah, sure it is. not saying those can't be great stories, but let's not kid each other, either, eh?
is saving the world too abstract? no, i don't think so. it's abstract if you make it that way, imo, and you do that by not making the reader connect with the place. this is where your world-building skillz come into play.
your story sounds to me as if it revolves around one battle that needs to be fought as part of the whole, not the whole itself? one piece of the puzzle, as it were.
i think there is an emotional core to saving the world. your characters live on that world, don't they? if you want to see them live, they'd better figure things out. most 'emotional cores' in sci-fi revolve around a scare factor, frightening the reader into believing it's very possible 'disease x' can reach you in your home, or that those facts your scientist gives are actual facts about earth-destroying meteors. rampaging goblins, well, that's harder, i guess, lol. but, that's why so many fantasies start off with the MC's village being burned to the ground.
too abstract? nah. too hard for people to wrap their minds around? after there's been so many save-the-world stories, why would you think that? if you think about it, quite a few if not most sci-fi has at least world-destruction implications because sci-fi writers often don't know how to do things small, lol. that is, heaven help us if those mecha-vampyres ever decide to go big time and make outright slaves of us all with vast areas of human cattle mooin' about. or if anyone ever finally figures out that they can see into the future by changing the date on their computer, well, that can easily lead to our destruction, can't it?, even if that's not the idea of the story. in sci-fi, whatever is there can get out of control and threaten the world, though that's not what you're specifically writing about. even in 'small' sci-fi, doesn't a lot of it depend on the implications of how bad things could potentially get?
troo, i don't think we should accuse world-saving stories as being dull: if they're dull to you, either you just don't like them or your friend isn't writing it well enough to make it entertaining. does he looove prologues and heaps of exposition? maybe he needs to bop over to SYW ~ i promise to be brutal but cruel.
it's funny, but i can't remember the last sci-fi movie i watched that didn't have the planet hanging in the balance, lol. maybe 'zathura,' if you consider that sci-fi. hm, 'monster house'?
i agree, though, none of it matters if the characters are crap.
none of this still explains sci-fi channel movies, though, which tend to be incomprehensibly stoopid. and not just, 'oops, i just bet my 401(k) on the cleveland browns to win the stanley cup next year' stoopid, but uwe boll dumb.