If you look at it from a strictly logical point of view, there has to be 1 person at the top of your theoretical "most compatible" list, out there somewhere, but it also depends on your criteria.
Do you include anyone who has ever lived or may live? or only people it is possible you would meet?
Can your soul mate be a gender your not attracted to? or must your soulmate be someone you can sleep with?
You start to ask these questions and it seems like a massive task and almost impossible to find your soulmate, but people swear they do and I think that's because anyone in the top 100 million of your list (theoretical "most compatible" list) is a pretty good match.
I also have to say I feel as if I have met someone pretty high on that list, meeting her was totally different and I'd had major crushes before but I was instantly hooked, for some reason, she felt the same and we have been together well over a year now, and things are amazing. We get along so well, we don't fight, though we do disagree (not heated) sometimes, but I see that as a good thing. We love and support each other and would I call her my soulmate? Yeah, I would. We are both completely committed to each other and knowing someone wants and loves you, as much as you want and love them is one of the greatest things you can have.