You should learn the language that most interests you. People who choose their target language based on say, the number of speakers, are people doomed to a deserved failure. You can only learn what you really, truly, intuitively want to learn. Any other reason for learning is a bad one. Listen to your heart and let it decide which of those you want to study. Don't ignore it just because you feel obligated by the supposed utility of some other language. It's YOUR life, no one else's, never forget that. No one else is going to live your life for you, so you shouldn't make your decisions and commitments (which learning a language is) based on what someone else tells you to do. If you learn languages you don't really want to learn, you'll die thinking about the langugages you really wanted to learn but never did because other people said it wasn't as useful. Every one of those languages will provide access to the others in one form or another, of course.
Finnish is not a Scandinavian language nor is Finland part of Scandinavia, BTW.
Finnish is not a Scandinavian language nor is Finland part of Scandinavia, BTW.