Two people who want to be in a relationship probably need to have similar outlooks on life or have similar goals. Something kind of broad which can keep them together. You need to have a certain level of comfort around someone and depending on what kind of person you are you might only need a little similarity or you might need more. I know that I would have a hard time in a relationship with someone who had very different morals than I do no matter how much I loved them.
Differences in taste, style, music, and things like that aren't going to keep two people apart if they have something else keeping them together. It's even important in your non-romantic relationships. My best friend and I are similar in a lot of ways, but when you look at our tastes and styles and hobbies we're almost on opposite ends of the... hobby spectrum. Or something. The point is, we're friends and we're different in a lot of ways, but if you stripped away a lot of things we'd be pretty similar and that similarity is what's kept us friends.