Provided the similarities were not vague and there were a lot of them, yes it would give me pause, but it would also give me pause in the opposite direction, given how earth and human centric the Bible is... how would their equivalent of Genesis read for instance; "In the beginning... in a galaxy far far away, God created the heavens and the earth, and created man in his own image. We on the other hand, he created in the image of his backside..." 
So in that respect I don't see how it could improve the credibility of the Bible. So assuming there were enough similarities, I'd be more likely wonder if there was anything universal about that story... that it contained aspects likely to be independently reached in any human-like society, similar to how civilizations the world over, however isolated they are from each other, all come up with the idea of the bow and arrow for instance.
So in that respect I don't see how it could improve the credibility of the Bible. So assuming there were enough similarities, I'd be more likely wonder if there was anything universal about that story... that it contained aspects likely to be independently reached in any human-like society, similar to how civilizations the world over, however isolated they are from each other, all come up with the idea of the bow and arrow for instance.
