When an elite intergalactic soldier on a secret mission to Earth discovers a plot hatched between a greedy cabal and his greatest alien enemy, he has no choice but to use all his combat skills to try and save the human race.

Thanks a lot you heat the point!

You need to be specific - aliens trying to destroy earth isn't fresh enough. What are they planning, and what must your protagonist do to stop them? This is what is going to determine whether your concept stands apart from the pack.

To continue my point. If a writer's story has a giant meteor that could destroy the earth, and a bickering couple who's relationship is on the rocks... I would lead with the giant world destroying meteor.

In your logline you say the lead, "discovers a plot." Telling us what that plot is, will up the stake and peak curiosity in the reader.

The more dangers and the higher the stakes for the lead character in the logline, the more the reader will be interested in your story.